feat(app): 服务端历史行首缩略图 + 上传中心空态引导至服务端历史

- UploadSessionPhoto 解析可选 preview；历史行首有 thumb 渲染 PhotoThumbnail
 （SizedBox 定寸——Row 内裸 AspectRatio 无界约束），缺省回退中性占位
- 上传中心整体空态加「仅本机存储」说明 + 「查看服务端历史」tonal 按钮
 （与右上 History 同路由）；「需关注」空态保持专属文案不加引导
- l10n 增 queueEmptyDeviceHint / queueViewServerHistory

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

apps/mobile/lib/pages/server_history_page.dart

@@ -30,6 +30,7 @@ import '../features/uploads/models.dart';
 import '../features/uploads/queue_controller.dart';
 import '../l10n/app_localizations.dart';
 import '../ui/components/empty_state.dart';
+import '../ui/components/photo_thumbnail.dart';
 import '../ui/components/error_state.dart';
 import '../ui/components/state_badge.dart';
 import '../ui/tokens.dart';
@@ -381,20 +382,32 @@ class _ServerHistoryPageState extends ConsumerState<ServerHistoryPage> {
       child: Row(
         crossAxisAlignment: CrossAxisAlignment.center,
         children: [
-          // 契约无图片 URL——中性占位（不伪造缩略图）。
-          Container(
-            width: 48,
-            height: 48,
-            decoration: BoxDecoration(
-              color: theme.colorScheme.surfaceContainerHighest,
-              borderRadius: BorderRadius.circular(kRadiusBadge),
+          // 行首 48×48：有 preview（变体齐备且未隐藏/删除，服务端现签）→
+          // 真实缩略图；缺省 → 中性占位图标（不伪造缩略图）。SizedBox 定
+          // 尺寸——Row 内直接放 AspectRatio 是无界约束。
+          if (record.photo.preview?.thumb.url case final String thumbUrl)
+            SizedBox(
+              width: 48,
+              height: 48,
+              child: ClipRRect(
+                borderRadius: BorderRadius.circular(kRadiusBadge),
+                child: PhotoThumbnail(url: thumbUrl, aspectRatio: 1),
+              ),
+            )
+          else
+            Container(
+              width: 48,
+              height: 48,
+              decoration: BoxDecoration(
+                color: theme.colorScheme.surfaceContainerHighest,
+                borderRadius: BorderRadius.circular(kRadiusBadge),
+              ),
+              child: Icon(
+                Icons.cloud_done_outlined,
+                size: 24,
+                color: theme.colorScheme.onSurfaceVariant,
+              ),
             ),
-            child: Icon(
-              Icons.cloud_done_outlined,
-              size: 24,
-              color: theme.colorScheme.onSurfaceVariant,
-            ),
-          ),
           const SizedBox(width: kSpace12),
           Expanded(
             child: Column(