Investigate comments loading issue (Issue #4)

- Added debug logging to post_detail route to track comment loading
- Created migration script for poll source fields (max_posts, fetch_comments, priority)
- Migration adds default values to ensure comments are fetched

The issue may be that existing poll sources in database dont have fetch_comments field.
Migration needs to be run on server with database access.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app.py

@@ -552,7 +552,8 @@ def post_detail(post_id):
             
         # Get comments from cache
         comments = cached_comments.get(post_id, [])
-                
+        logger.info(f"Loading post {post_id}: found {len(comments)} comments")
+
         # Sort comments by timestamp
         comments.sort(key=lambda x: x.get('timestamp', 0))