fix(qml): 预览区放大 + AppState 加 QML_AUTO_LOGIN 调试模式

- 参考图 Card  preferredHeight 200 → 170
- 提示词+设置行 preferredHeight 320 → 290
- 预览 Card  minimumHeight 200 → 240（拿剩余空间，视觉更舒展）
- AppState: QML_AUTO_LOGIN=1 时默认登录态，调试时不必每次重启都过登录页

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

@@ -24,7 +24,9 @@ class AppState(QObject):
 
     def __init__(self):
         super().__init__()
-        self._logged_in = False
+        # PoC 调试：QML_AUTO_LOGIN=1 时直接登录态，免每次重启进程都发回车登录
+        import os
+        self._logged_in = os.environ.get("QML_AUTO_LOGIN", "") == "1"
         self._current_tab = 0
 
     @Property(bool, notify=loggedInChanged)

@@ -13,8 +13,8 @@ Item {
         // ===== 参考图片卡片 =====
         Card {
             Layout.fillWidth: true
-            Layout.preferredHeight: 200
-            Layout.minimumHeight: 180
+            Layout.preferredHeight: 170
+            Layout.minimumHeight: 160
 
             ColumnLayout {
                 anchors.fill: parent
@@ -72,8 +72,8 @@ Item {
         RowLayout {
             spacing: App.Theme.space4
             Layout.fillWidth: true
-            Layout.preferredHeight: 320
-            Layout.minimumHeight: 320
+            Layout.preferredHeight: 290
+            Layout.minimumHeight: 280
 
             // 提示词
             Card {
@@ -188,7 +188,7 @@ Item {
         Card {
             Layout.fillWidth: true
             Layout.fillHeight: true
-            Layout.minimumHeight: 200
+            Layout.minimumHeight: 240
 
             ColumnLayout {
                 anchors.fill: parent