Fix real-time message updates: use blocking Redis XREAD

The chat message list wasn't updating in real-time because XREAD was using
non-blocking mode, causing it to return immediately without waiting for new
messages.

Root cause:
- XREAD_TIMEOUT = 0 was converted to block=None (non-blocking)
- In old aioredis: timeout=0 meant "block forever"
- In new redis library: block=None means "non-blocking" (return immediately)
- This caused XREAD to constantly poll without waiting for messages

Fix:
- Changed to block=5000 (5 seconds) for proper blocking behavior
- XREAD now waits up to 5 seconds for new messages before returning
- Messages now appear in real-time for all connected users

Tested:
- Users connecting to the same room see each other's messages immediately
- Message list updates within milliseconds of sending
- No more need to refresh or reconnect to see new messages

Author: claude

chat.py

@@ -135,7 +135,7 @@ async def ws_send_moderator(websocket: WebSocket, chat_info: dict):
             events = await pool.xread(
                 streams=latest_ids,
                 count=XREAD_COUNT,
-                block=XREAD_TIMEOUT if XREAD_TIMEOUT > 0 else None
+                block=5000  # Block for 5 seconds waiting for new messages
             )
             for stream, messages in events:
                 for e_id, e in messages:
@@ -182,7 +182,7 @@ async def ws_send(websocket: WebSocket, chat_info: dict):
                 events = await pool.xread(
                     streams=latest_ids,
                     count=XREAD_COUNT,
-                    block=XREAD_TIMEOUT if XREAD_TIMEOUT > 0 else None
+                    block=5000  # Block for 5 seconds waiting for new messages
                 )
                 for stream, messages in events:
                     for e_id, e in messages: