Blur gallery images by default, sync progress UI, and add chat/monitor tests

- Blur NSFW media gallery images until hover/reveal
- Surface chat sync progress in the dashboard header
- Extend chat service, cache, and monitor with delta-media handling
- Add tests for chat cooldown, delta media, and monitor flows

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/monitor.test.ts

@@ -156,6 +156,70 @@ describe('MonitorService', () => {
     expect(Array.isArray(result)).toBe(true);
   });
 
+  it('prefers a recent post over an older one when prioritizeRecentPosts is enabled', async () => {
+    const now = Math.floor(Date.now() / 1000);
+    const oldPost: RedditPost = {
+      id: 't3_old', subreddit: 'sub1', author: 'u_old', title: 'Old',
+      url: 'http://example.com/old.jpg', permalink: '/r/sub1/old', thumbnail: '',
+      is_self: false, created_utc: now - 7200, over_18: false, spoiler: false,
+    };
+    const recentPost: RedditPost = {
+      id: 't3_new', subreddit: 'sub2', author: 'u_new', title: 'New',
+      url: 'http://example.com/new.jpg', permalink: '/r/sub2/new', thumbnail: '',
+      is_self: false, created_utc: now - 600, over_18: false, spoiler: false,
+    };
+
+    const redditApi = {
+      getNewPosts: vi.fn(async (sub: string) =>
+        sub === 'sub1' ? [oldPost] : [recentPost],
+      ),
+      getImageUrl: vi.fn(),
+      getPostUrl: vi.fn(),
+      isSellerProfile: vi.fn(async () => false),
+    } as unknown as RedditApiClient;
+    const postsRepo = createMockPostsRepo();
+    const messagesRepo = createMockMessagesRepo();
+    const config = getTestConfig({
+      reddit: {
+        subreddits: [{ name: 'sub1', type: 'image' }, { name: 'sub2', type: 'image' }],
+        prioritizeRecentPosts: true,
+        recentWindowMinutes: 60,
+      },
+    });
+
+    monitor = new MonitorService(redditApi, postsRepo, messagesRepo, config, logger, 0);
+    const result = await monitor.getUnprocessedPosts();
+
+    expect(result.length).toBe(1);
+    expect(result[0].id).toBe('t3_new');
+  });
+
+  it('falls back to the newest older post when no recent posts exist', async () => {
+    const now = Math.floor(Date.now() / 1000);
+    const oldPost: RedditPost = {
+      id: 't3_old', subreddit: 'sub1', author: 'u_old', title: 'Old',
+      url: 'http://example.com/old.jpg', permalink: '/r/sub1/old', thumbnail: '',
+      is_self: false, created_utc: now - 7200, over_18: false, spoiler: false,
+    };
+
+    const redditApi = createMockRedditApi([oldPost]);
+    const postsRepo = createMockPostsRepo();
+    const messagesRepo = createMockMessagesRepo();
+    const config = getTestConfig({
+      reddit: {
+        subreddits: [{ name: 'sub1', type: 'image' }],
+        prioritizeRecentPosts: true,
+        recentWindowMinutes: 60,
+      },
+    });
+
+    monitor = new MonitorService(redditApi, postsRepo, messagesRepo, config, logger, 0);
+    const result = await monitor.getUnprocessedPosts();
+
+    expect(result.length).toBe(1);
+    expect(result[0].id).toBe('t3_old');
+  });
+
   it('returns empty array when no subreddits have valid posts', async () => {
     const redditApi = createMockRedditApi([]);
     const postsRepo = createMockPostsRepo();