refactor: streamline post sync, fix image gallery, and clean up chat screen

- **Post sync optimization**: Clear store immediately when params change to prevent flashing old posts; replace instead of merge on refresh
- **ImageGallery fix**: Use idempotent download option, migrate to Asset.create() API, fix Android file path requirement, ensure proper cleanup
- **UserProfileScreen**: Add ImageGallery for post image viewing with consistent implementation
- **SearchScreen**: Add entrance animation and empty state
- **ChatScreen**: Remove unused state variables (lastSeq, firstSeq, isProgrammaticScrollRef) and dead imports

src/screens/profile/UserProfileScreen.tsx

@@ -16,7 +16,8 @@ import { SafeAreaView } from 'react-native-safe-area-context';
 import { useAppColors } from '../../theme';
 import { Post } from '../../types';
 import { PostCard, TabBar, UserProfileHeader } from '../../components/business';
-import { Loading, EmptyState, ResponsiveContainer } from '../../components/common';
+import type { PostCardAction } from '../../components/business/PostCard';
+import { Loading, EmptyState, ResponsiveContainer, ImageGallery, ImageGridItem } from '../../components/common';
 import { useResponsive } from '../../hooks';
 import { useUserProfile, ProfileMode, TABS, TAB_ICONS, createSharedProfileStyles } from './useUserProfile';
 
@@ -116,6 +117,39 @@ export const UserProfileScreen: React.FC<UserProfileScreenProps> = ({ mode, user
     currentUser,
   } = useUserProfile({ mode, userId, isDesktop, isTablet });
 
+  // 图片查看器状态（与 HomeScreen / PostDetailScreen 一致）
+  const [showImageViewer, setShowImageViewer] = useState(false);
+  const [postImages, setPostImages] = useState<ImageGridItem[]>([]);
+  const [selectedImageIndex, setSelectedImageIndex] = useState(0);
+
+  const closeImageViewer = useCallback(() => setShowImageViewer(false), []);
+  const stableGalleryImages = useMemo(
+    () =>
+      postImages.map((img, i) => ({
+        id: img.id || img.url || `img-${i}`,
+        url: img.url || img.uri || '',
+      })),
+    [postImages]
+  );
+
+  // 包装 handlePostAction：在 hook 通用逻辑之上处理 imagePress
+  const onPostAction = useCallback(
+    (post: Post, action: PostCardAction) => {
+      if (action.type === 'imagePress') {
+        const images = action.payload?.images;
+        const imageIndex = action.payload?.imageIndex;
+        if (images && imageIndex !== undefined) {
+          setPostImages(images);
+          setSelectedImageIndex(imageIndex);
+          setShowImageViewer(true);
+        }
+        return;
+      }
+      handlePostAction(post, action);
+    },
+    [handlePostAction]
+  );
+
   // 当前显示的帖子列表
   const currentPosts = activeTab === 0 ? posts : favorites;
 
@@ -130,12 +164,12 @@ export const UserProfileScreen: React.FC<UserProfileScreenProps> = ({ mode, user
       ]}>
         <PostCard
           post={item}
-          onAction={(action) => handlePostAction(item, action)}
+          onAction={(action) => onPostAction(item, action)}
           isPostAuthor={isPostAuthor}
         />
       </View>
     );
-  }, [currentUser?.id, handlePostAction, currentPosts.length]);
+  }, [currentUser?.id, onPostAction, currentPosts.length]);
 
   const postKeyExtractor = useCallback((item: Post) => item.id, []);
 
@@ -269,6 +303,15 @@ export const UserProfileScreen: React.FC<UserProfileScreenProps> = ({ mode, user
             </View>
           </View>
         </ResponsiveContainer>
+
+        {/* 图片查看器 */}
+        <ImageGallery
+          visible={showImageViewer}
+          images={stableGalleryImages}
+          initialIndex={selectedImageIndex}
+          onClose={closeImageViewer}
+          enableSave
+        />
       </SafeAreaView>
     );
   }
@@ -310,6 +353,15 @@ export const UserProfileScreen: React.FC<UserProfileScreenProps> = ({ mode, user
         }
         drawDistance={250}
       />
+
+      {/* 图片查看器 */}
+      <ImageGallery
+        visible={showImageViewer}
+        images={stableGalleryImages}
+        initialIndex={selectedImageIndex}
+        onClose={closeImageViewer}
+        enableSave
+      />
     </SafeAreaView>
   );
 };