Handle deleted posts that return InternalServerError

Bluesky's getPostThread API sometimes returns InternalServerError
instead of NotFound for deleted posts. Now we verify with getRecord
to confirm the post is actually deleted before removing from queue.

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

Co-Authored-By: Claude <[e-mail]>

bsky.py

···
             if 'NotFound' in error_str or 'Post not found' in error_str:
                 logger.warning(f"Post not found for URI {uri}, removing from queue")
                 return True  # Return True to remove from queue
+            elif 'InternalServerError' in error_str:
+                # Bluesky sometimes returns InternalServerError for deleted posts
+                # Verify if post actually exists using getRecord
+                try:
+                    parts = uri.replace('at://', '').split('/')
+                    repo, collection, rkey = parts[0], parts[1], parts[2]
+                    atproto_client.com.atproto.repo.get_record({
+                        'repo': repo, 'collection': collection, 'rkey': rkey
+                    })
+                    # Post exists, this is a real server error - re-raise
+                    logger.error(f"Error fetching thread (post exists, server error): {e}")
+                    raise
+                except Exception as verify_e:
+                    if 'RecordNotFound' in str(verify_e) or 'not found' in str(verify_e).lower():
+                        logger.warning(f"Post deleted (verified via getRecord), removing from queue: {uri}")
+                        return True  # Remove from queue
+                    # Some other verification error, re-raise original
+                    logger.error(f"Error fetching thread: {e}")
+                    raise
             else:
                 # Re-raise other errors
                 logger.error(f"Error fetching thread: {e}")