Show Reddit post age in conversations

tests/repositories.test.ts

@@ -31,6 +31,7 @@ describe('PostsRepository', () => {
       title: 'Test Post',
       postUrl: 'https://www.reddit.com/r/test/comments/post1/test_post/',
       imageUrl: 'http://example.com/img.jpg',
+      postCreatedAt: 1_700_000_000_000,
       processedAt: Date.now(),
     });
 
@@ -42,6 +43,7 @@ describe('PostsRepository', () => {
     expect(post!.title).toBe('Test Post');
     expect(post!.postUrl).toBe('https://www.reddit.com/r/test/comments/post1/test_post/');
     expect(post!.imageUrl).toBe('http://example.com/img.jpg');
+    expect(post!.postCreatedAt).toBe(1_700_000_000_000);
     expect(post!.messageSent).toBe(false);
     expect(post!.imageAnalysis).toBeNull();
     expect(post!.error).toBeNull();
@@ -314,6 +316,7 @@ describe('MessagesRepository', () => {
       title: 'Second post',
       postUrl: 'https://www.reddit.com/r/gonewild/comments/post-b/second_post/',
       imageUrl: null,
+      postCreatedAt: 1_700_000_000_000,
       processedAt: Date.now(),
     });
 
@@ -327,6 +330,7 @@ describe('MessagesRepository', () => {
     expect(latest!.subreddit).toBe('gonewild');
     expect(latest!.postTitle).toBe('Second post');
     expect(latest!.postUrl).toBe('https://www.reddit.com/r/gonewild/comments/post-b/second_post/');
+    expect(latest!.postCreatedAt).toBe(1_700_000_000_000);
     expect(messagesRepo.getByChatRoomId('room-b')).toMatchObject({ postId: 'post-b', postTitle: 'Second post' });
 
     expect(messagesRepo.getLatestByRecipient('ALICE')).toBeDefined();