feat(app): P0 batch 1 — photo viewer zoom, camera lifecycle, image memory management

P0-2 查看器缩放：InteractiveViewer（5x max，放大后平移，1x 时穿透到
  PageView 滑动切页）
P0-3 相机后台释放：WidgetsBindingObserver——paused 时 dispose（省电+
  隐私指示灯），resumed 时重开（沿用前后摄/闪光灯偏好）
P0-6 图片内存管理：PhotoThumbnail 加 maxCacheWidth 参数——网格/列表
  缩略图限制解码宽度（600/400px），查看器大图不限

397/397 全绿、analyze 0

Co-Authored-By: Claude Code <noreply@anthropic.com>

apps/mobile/lib/pages/album_photos_page.dart

@@ -50,8 +50,8 @@ enum PhotoGridFilter {
   final String wire;
 
   /// 本地过滤（服务端无 processingState 查询参数）。
-  bool get isLocal => this == PhotoGridFilter.processing ||
-      this == PhotoGridFilter.failed;
+  bool get isLocal =>
+      this == PhotoGridFilter.processing || this == PhotoGridFilter.failed;
 }
 
 /// 一页数据的请求规格（刷新签名 URL 时按原参数重取该页）。
@@ -83,12 +83,12 @@ class PhotoGridController extends ChangeNotifier {
     required Future<Session?> Function() readSession,
     required this.albumId,
     this.pageSize = 20,
-  })  // 私有字段不能作 initializing formal（外部调用方无法传私有名），
-      // 参数名保持公开语义，忽略该风格提示。
-      // ignore: prefer_initializing_formals
-      : _api = api,
-        // ignore: prefer_initializing_formals
-        _readSession = readSession;
+  }) // 私有字段不能作 initializing formal（外部调用方无法传私有名），
+    // 参数名保持公开语义，忽略该风格提示。
+    // ignore: prefer_initializing_formals
+    : _api = api,
+       // ignore: prefer_initializing_formals
+       _readSession = readSession;
 
   final ApiClient _api;
   final Future<Session?> Function() _readSession;
@@ -115,12 +115,16 @@ class PhotoGridController extends ChangeNotifier {
 
   /// 当前筛选下应显示的条目。
   List<AdminPhoto> get visibleItems => switch (_filter) {
-    PhotoGridFilter.processing => _items
-        .where((p) => p.processingState != PhotoProcessingState.ready)
-        .toList(growable: false),
-    PhotoGridFilter.failed => _items
-        .where((p) => p.processingState == PhotoProcessingState.processingFailed)
-        .toList(growable: false),
+    PhotoGridFilter.processing =>
+      _items
+          .where((p) => p.processingState != PhotoProcessingState.ready)
+          .toList(growable: false),
+    PhotoGridFilter.failed =>
+      _items
+          .where(
+            (p) => p.processingState == PhotoProcessingState.processingFailed,
+          )
+          .toList(growable: false),
     _ => _items,
   };
 
@@ -362,26 +366,25 @@ class PhotoGridController extends ChangeNotifier {
   }
 
   /// 删除（软删除，云端照片将被移除；权限同隐藏）。
-  Future<void> deletePhoto(AdminPhoto photo) =>
-      _api.deletePhoto(photo.photoId);
+  Future<void> deletePhoto(AdminPhoto photo) => _api.deletePhoto(photo.photoId);
 
   AdminPhoto _withRecord(AdminPhoto src, PhotoRecord rec) => AdminPhoto(
-        uploader: src.uploader,
-        preview: src.preview,
-        photoId: rec.photoId,
-        albumId: rec.albumId,
-        categoryId: rec.categoryId,
-        uploaderId: rec.uploaderId,
-        visibility: rec.visibility,
-        processingState: rec.processingState,
-        bytes: rec.bytes,
-        width: rec.width,
-        height: rec.height,
-        shotAt: rec.shotAt,
-        uploadedAt: rec.uploadedAt,
-        publishedAt: rec.publishedAt,
-        likeCount: rec.likeCount,
-      );
+    uploader: src.uploader,
+    preview: src.preview,
+    photoId: rec.photoId,
+    albumId: rec.albumId,
+    categoryId: rec.categoryId,
+    uploaderId: rec.uploaderId,
+    visibility: rec.visibility,
+    processingState: rec.processingState,
+    bytes: rec.bytes,
+    width: rec.width,
+    height: rec.height,
+    shotAt: rec.shotAt,
+    uploadedAt: rec.uploadedAt,
+    publishedAt: rec.publishedAt,
+    likeCount: rec.likeCount,
+  );
 
   /// 覆盖 [index] 的页规格（删除导致边界漂移时按近似页处理）。
   _PageSpec? _pageForIndex(int index) {
@@ -406,12 +409,12 @@ class PhotoGridController extends ChangeNotifier {
     PhotoVisibility? visibility,
     int? limit,
   }) => _api.listAlbumPhotos(
-        albumId,
-        scope: scope,
-        visibility: visibility,
-        cursor: cursor,
-        limit: limit,
-      );
+    albumId,
+    scope: scope,
+    visibility: visibility,
+    cursor: cursor,
+    limit: limit,
+  );
 }
 
 /// 照片管理网格页（从详情页携带 [album] 进入，时间按相册时区展示）。
@@ -654,7 +657,8 @@ class _AlbumPhotosBody extends StatelessWidget {
   /// 请求）。
   void _maybeLoadMore(int index, int visibleCount) {
     final nearEnd = index >= visibleCount - 6;
-    final localStarved = controller.filter.isLocal &&
+    final localStarved =
+        controller.filter.isLocal &&
         visibleCount < 9 &&
         controller.items.length < _localFilterAutoLoadCap;
     if ((nearEnd || localStarved) &&
@@ -662,7 +666,9 @@ class _AlbumPhotosBody extends StatelessWidget {
         !controller.loadingMore &&
         !controller.loading &&
         !controller.loadMoreFailed) {
-      WidgetsBinding.instance.addPostFrameCallback((_) => controller.loadMore());
+      WidgetsBinding.instance.addPostFrameCallback(
+        (_) => controller.loadMore(),
+      );
     }
   }
 
@@ -705,7 +711,9 @@ class _PhotoFilterChip extends StatelessWidget {
       ),
       selectedColor: theme.colorScheme.primary,
       labelStyle: theme.textTheme.labelLarge?.copyWith(
-        color: selected ? theme.colorScheme.onPrimary : theme.colorScheme.onSurface,
+        color: selected
+            ? theme.colorScheme.onPrimary
+            : theme.colorScheme.onSurface,
         fontWeight: FontWeight.w600,
       ),
       padding: const EdgeInsets.symmetric(horizontal: kSpace8),
@@ -756,6 +764,7 @@ class _PhotoGridTile extends StatelessWidget {
             PhotoThumbnail(
               url: photo.preview?.thumb.url,
               aspectRatio: 1,
+              maxCacheWidth: 400,
             ),
             if (badge != null)
               Positioned(