refactor: 业务核心从 image_generator.py 拆到 core/

5082 行的怪兽塞了 12 个类（数据库/历史/Worker/词库/UI），现在按职责拆开：

  core/paths.py       get_app_data_path + save_png_with_validation + 启动迁移
  core/database.py    DatabaseManager + hash_password
  core/history.py     HistoryItem + HistoryListModel + HistoryManager
  core/generation.py  ImageGenerationWorker + Gemini 模型常量
  core/jewelry.py     DEFAULT_JEWELRY_LIBRARY + JewelryLibraryManager + PromptAssembler

image_generator.py 5082 → 3781 行，剩下全是 QWidget UI 类
（LoginDialog / DraggableThumbnail / DragDropScrollArea / ImageGeneratorWindow /
StyleDesignerTab + utils + main），task #19 QML 全量切换后整体删除。

外部消费者改 import：
  task_queue.py / temp_clean.py: from image_generator → from core.generation
  image_generator.py 顶部 from core.* 引入，LoginDialog 等内部代码无感知

冒烟测试：image_generator/task_queue/core 各自 import 通过，类身份正确。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

+"""业务核心模块。
+
+从 image_generator.py 拆出，保留 QWidget UI 类在原文件供 task #19 整删。
+QML 桥层和外部模块直接 import core.* 而不是 image_generator。
+"""

+"""数据库连接 + 用户认证。
+
+DatabaseManager 只负责 MySQL 连接和 user table 的 SHA256 密码核验。
+db_config 由 config_util 加载并传入；本模块不读 config 文件本身。
+"""
+import hashlib
+import logging
+
+import pymysql
+
+
+def hash_password(password: str) -> str:
+    """使用 SHA256 哈希密码"""
+    return hashlib.sha256(password.encode('utf-8')).hexdigest()
+
+
+class DatabaseManager:
+    """数据库连接管理类"""
+
+    def __init__(self, db_config):
+        self.config = db_config
+        self.logger = logging.getLogger(__name__)
+
+    def authenticate(self, username, password):
+        """
+        验证用户凭证
+        返回: (success: bool, message: str)
+        """
+        try:
+            self.logger.info(f"开始用户认证: {username}")
+
+            password_hash = hash_password(password)
+
+            self.logger.debug(f"连接数据库: {self.config['host']}:{self.config.get('port', 3306)}")
+            conn = pymysql.connect(
+                host=self.config['host'],
+                port=self.config.get('port', 3306),
+                user=self.config['user'],
+                password=self.config['password'],
+                database=self.config['database'],
+                connect_timeout=5
+            )
+
+            try:
+                with conn.cursor() as cursor:
+                    sql = f"SELECT * FROM {self.config['table']} WHERE user_name=%s AND passwd=%s AND status='active'"
+                    cursor.execute(sql, (username, password_hash))
+                    result = cursor.fetchone()
+
+                    if result:
+                        self.logger.info(f"用户认证成功: {username}")
+                        return True, "认证成功"
+                    else:
+                        self.logger.warning(f"用户认证失败: {username} - 用户名或密码错误")
+                        return False, "用户名或密码错误"
+            finally:
+                conn.close()
+
+        except pymysql.OperationalError as e:
+            error_msg = "无法连接到服务器,请检查网络连接"
+            self.logger.error(f"数据库连接失败: {e}")
+            return False, error_msg
+        except Exception as e:
+            error_msg = f"认证失败: {str(e)}"
+            self.logger.error(f"认证过程异常: {e}")
+            return False, error_msg

+"""图像生成 Worker + Gemini 模型常量。
+
+ImageGenerationWorker 是 QThread，由 TaskQueueManager 拉起执行单条生成任务。
+任务参数（prompt / 参考图 / aspect_ratio / image_size / model）从队列传入，
+完成后通过 finished/error/progress 信号回报。
+"""
+import base64
+import logging
+import os
+from typing import Optional
+
+from PySide6.QtCore import QThread, Signal
+from google import genai
+from google.genai import types
+
+
+# 生成模式 -> Gemini 模型 ID 映射（单一真相源，消除原先两处 get_selected_model 复制粘贴）
+# 极速模式：Nano Banana 2 (Gemini 3.1 Flash Image), 指令遵循强于 2.5-flash-image
+# 慢速模式：Nano Banana Pro (Gemini 3 Pro Image Preview)
+MODEL_BY_MODE = {
+    "极速模式": "gemini-3.1-flash-image-preview",
+    "慢速模式": "gemini-3-pro-image-preview",
+}
+MODEL_PRO = MODEL_BY_MODE["慢速模式"]  # 用于 Worker 中判断是否支持 image_size 参数
+
+# Nano Banana 2 (Flash) 独占的宽高比 —— Pro 不支持，选中这些时需提示切换到极速模式
+FLASH_ONLY_ASPECT_RATIOS = {"1:4", "4:1", "1:8", "8:1"}
+
+
+class ImageGenerationWorker(QThread):
+    """Worker thread for image generation"""
+    finished = Signal(bytes, str, list, str, str,
+                      str)  # image_bytes, prompt, reference_images, aspect_ratio, image_size, model
+    error = Signal(str)
+    progress = Signal(str)
+
+    def __init__(self, api_key, prompt, images, aspect_ratio, image_size, model=MODEL_PRO):
+        super().__init__()
+        self.logger = logging.getLogger(__name__)
+        self.api_key = api_key
+        self.prompt = prompt
+        self.images = images
+        self.aspect_ratio = aspect_ratio
+        self.image_size = image_size
+        self.model = model
+
+        # 审计元信息：供 TaskQueueManager 在信号回调中读取
+        self.finish_reason: Optional[str] = None
+
+        self.logger.info(f"图片生成任务初始化 - 模型: {model}, 尺寸: {image_size}, 宽高比: {aspect_ratio}")
+
+    def _extract_finish_reason(self, response) -> Optional[str]:
+        """从 Gemini 响应提取 finish_reason，失败返回 None（不抛异常）。"""
+        try:
+            fr = response.candidates[0].finish_reason
+            if fr is None:
+                return None
+            name = getattr(fr, "name", None)
+            return name if name else str(fr)
+        except Exception:
+            return None
+
+    def run(self):
+        """Execute image generation in background thread"""
+        try:
+            self.logger.info("开始图片生成任务")
+
+            if not self.prompt:
+                self.logger.error("图片描述为空")
+                self.error.emit("请输入图片描述！")
+                return
+
+            if not self.api_key:
+                self.logger.error("API密钥为空")
+                self.error.emit("未找到API密钥，请在config.json中配置！")
+                return
+
+            self.progress.emit("正在连接 Gemini API...")
+            self.logger.debug("正在连接 Gemini API")
+
+            client = genai.Client(api_key=self.api_key)
+
+            content_parts = [self.prompt]
+
+            for img_path in self.images:
+                with open(img_path, 'rb') as f:
+                    img_data = f.read()
+
+                mime_type = "image/png"
+                if img_path.lower().endswith(('.jpg', '.jpeg')):
+                    mime_type = "image/jpeg"
+
+                content_parts.append(
+                    types.Part.from_bytes(
+                        data=img_data,
+                        mime_type=mime_type
+                    )
+                )
+
+            self.progress.emit("正在生成图片...")
+
+            # 当前使用的两个模型都支持 aspect_ratio + image_size：
+            #   - gemini-3.1-flash-image-preview (Nano Banana 2): 512/1K/2K/4K + 14 种 ratio
+            #   - gemini-3-pro-image-preview (Nano Banana Pro):   1K/2K/4K
+            config = types.GenerateContentConfig(
+                response_modalities=["TEXT", "IMAGE"],
+                image_config=types.ImageConfig(
+                    aspect_ratio=self.aspect_ratio,
+                    image_size=self.image_size
+                )
+            )
+
+            response = client.models.generate_content(
+                model=self.model,
+                contents=content_parts,
+                config=config
+            )
+            self.finish_reason = self._extract_finish_reason(response)
+
+            text_fragments = []
+            parts = response.parts or []
+            for part in parts:
+                if hasattr(part, 'inline_data') and part.inline_data:
+                    if isinstance(part.inline_data.data, bytes):
+                        image_bytes = part.inline_data.data
+                    else:
+                        image_bytes = base64.b64decode(part.inline_data.data)
+
+                    reference_images_bytes = []
+                    for img_path in self.images:
+                        if img_path and os.path.exists(img_path):
+                            with open(img_path, 'rb') as f:
+                                reference_images_bytes.append(f.read())
+                        else:
+                            reference_images_bytes.append(b'')
+
+                    self.logger.info(
+                        f"图片生成成功 - 模型: {self.model}, 尺寸: {self.image_size}, "
+                        f"finish_reason={self.finish_reason}"
+                    )
+                    self.finished.emit(image_bytes, self.prompt, reference_images_bytes,
+                                       self.aspect_ratio, self.image_size, self.model)
+                    return
+                if getattr(part, 'text', None):
+                    text_fragments.append(part.text)
+
+            detail = " | ".join(t for t in text_fragments if t).strip()
+            error_msg = f"响应中没有图片数据 (finish_reason={self.finish_reason})"
+            if detail:
+                error_msg += f"\n模型说明: {detail}"
+            self.logger.error(error_msg)
+            self.error.emit(error_msg)
+
+        except Exception as e:
+            error_msg = f"图片生成异常: {e}"
+            self.logger.error(error_msg, exc_info=True)
+            self.error.emit(error_msg)

+"""应用数据路径 + 图片格式校验工具。
+
+跨平台数据目录探测（macOS .app 包外存储 / Windows APPDATA / 开发环境同目录），
+PNG/JPEG 格式回正（Pillow 重写防止伪装 MIME）。
+"""
+import io
+import logging
+import os
+import platform
+import shutil
+import sys
+from pathlib import Path
+
+
+def _migrate_data_from_app_bundle(target_path: Path):
+    """将 .app 内部的旧数据迁移到外部目录（仅 macOS 打包环境）"""
+    if not (getattr(sys, 'frozen', False) and platform.system() == "Darwin"):
+        return
+
+    old_path = Path(sys.executable).parent / "images"
+    if not old_path.exists() or old_path == target_path:
+        return
+
+    old_files = list(old_path.rglob("*"))
+    if not old_files:
+        return
+
+    try:
+        target_path.mkdir(parents=True, exist_ok=True)
+        migrated = 0
+        for src_file in old_path.rglob("*"):
+            if src_file.is_file():
+                rel_path = src_file.relative_to(old_path)
+                dst_file = target_path / rel_path
+                if not dst_file.exists():
+                    dst_file.parent.mkdir(parents=True, exist_ok=True)
+                    shutil.copy2(str(src_file), str(dst_file))
+                    migrated += 1
+        print(f"已从 .app 内部迁移 {migrated} 个文件到: {target_path}")
+    except Exception as e:
+        print(f"数据迁移失败（不影响使用）: {e}")
+
+
+def get_app_data_path() -> Path:
+    """获取应用数据存储路径 - 智能选择"""
+
+    def get_candidate_paths():
+        system = platform.system()
+        candidates = []
+
+        if getattr(sys, 'frozen', False) and system == "Darwin":
+            candidates.append(Path.home() / "Library/Application Support/ZB100ImageGenerator/images")
+        elif getattr(sys, 'frozen', False):
+            candidates.append(Path(sys.executable).parent / "images")
+        else:
+            # 开发环境：保持和老路径一致 —— 项目根目录下的 images/
+            # __file__ 在 core/，需要往上一级
+            candidates.append(Path(__file__).resolve().parent.parent / "images")
+
+        if system == "Darwin":
+            candidates.append(Path.home() / "Library/Application Support/ZB100ImageGenerator/images")
+            candidates.append(Path.home() / "Documents/ZB100ImageGenerator/images")
+        elif system == "Windows":
+            candidates.append(Path(os.environ.get("APPDATA", "")) / "ZB100ImageGenerator/images")
+            candidates.append(Path.home() / "Documents/ZB100ImageGenerator/images")
+        else:
+            candidates.append(Path.home() / ".config/zb100imagegenerator/images")
+            candidates.append(Path.home() / "Documents/ZB100ImageGenerator/images")
+
+        return candidates
+
+    def test_path_write_access(path: Path) -> bool:
+        try:
+            path.mkdir(parents=True, exist_ok=True)
+            test_file = path / ".write_test"
+            test_file.write_text("test")
+            test_file.unlink()
+            return True
+        except (PermissionError, OSError) as e:
+            print(f"路径 {path} 无写入权限: {e}")
+            return False
+        except Exception as e:
+            print(f"路径 {path} 测试失败: {e}")
+            return False
+
+    candidates = get_candidate_paths()
+
+    for path in candidates:
+        if test_path_write_access(path):
+            _migrate_data_from_app_bundle(path)
+            print(f"使用图片存储路径: {path}")
+            return path
+
+    fallback_path = get_candidate_paths()[0]
+    try:
+        fallback_path.mkdir(parents=True, exist_ok=True)
+        print(f"使用备选路径: {fallback_path}")
+        return fallback_path
+    except Exception as e:
+        print(f"警告: 无法创建存储路径，将在当前目录操作: {e}")
+        return Path.cwd() / "images"
+
+
+def save_png_with_validation(file_path: str, image_bytes: bytes) -> bool:
+    """使用 Pillow 验证并重写 PNG/JPEG，确保 MIME 与扩展名一致。
+
+    返回 True 表示 Pillow 处理成功；False 表示 Pillow 不可用或处理失败，
+    调用方应回退到原始 write_bytes。
+    """
+    try:
+        from PIL import Image
+
+        with Image.open(io.BytesIO(image_bytes)) as img:
+            file_format = img.format
+            if file_format == 'JPEG':
+                logger = logging.getLogger(__name__)
+                logger.info(f"检测到伪装PNG的JPEG文件，实际格式: {file_format}")
+
+            save_format = 'PNG' if file_path.lower().endswith('.png') else 'JPEG'
+
+            if file_format and file_format != save_format:
+                logger = logging.getLogger(__name__)
+                logger.info(f"执行格式转换: {file_format} -> {save_format}")
+
+                if save_format == 'PNG':
+                    if img.mode not in ['RGBA', 'RGB', 'L']:
+                        if img.mode == 'P':
+                            img = img.convert('RGBA')
+                        elif img.mode == 'LA':
+                            img = img.convert('RGBA')
+                        else:
+                            img = img.convert('RGBA')
+                elif save_format == 'JPEG':
+                    if img.mode in ['RGBA', 'P']:
+                        img = img.convert('RGB')
+                    elif img.mode == 'L':
+                        img = img.convert('RGB')
+
+            img.save(file_path, save_format, optimize=True)
+
+        logger = logging.getLogger(__name__)
+        logger.info(f"图片格式验证成功: {file_path}, 保存格式: {save_format}")
+        return True
+
+    except ImportError:
+        logger = logging.getLogger(__name__)
+        logger.warning("Pillow库不可用，使用原始保存方法")
+        return False
+
+    except Exception as e:
+        logger = logging.getLogger(__name__)
+        logger.warning(f"Pillow处理失败，使用原始保存方法: {e}")
+        return False

@@ -192,7 +192,7 @@ class TaskQueueManager(QObject):
         self.logger.info(f"开始处理任务: {task_id[:8]}")
 
         # 导入 ImageGenerationWorker
-        from image_generator import ImageGenerationWorker
+        from core.generation import ImageGenerationWorker
 
         # 创建 worker
         self._current_worker = ImageGenerationWorker(

@@ -177,7 +177,7 @@ class TaskQueueManager(QObject):
         self.logger.info(f"开始处理任务: {task_id[:8]}")
 
         # 导入 ImageGenerationWorker
-        from image_generator import ImageGenerationWorker
+        from core.generation import ImageGenerationWorker
 
         # 创建 worker
         self._current_worker = ImageGenerationWorker(