feat(redis): refactor Redis configuration to use multiple logical databases

- Updated default REDIS_URL to remove explicit /0 suffix
- Added dedicated Redis clients:
  - db0: general cache (redis_client)
  - db1: message cache (redis_message_client)
  - db2: binary storage (redis_binary_client)
  - db3: rate limiting (redis_rate_limit_client)
- Updated configuration, Docker files, and main startup lifecycle accordingly
- Replaced `get_redis()` usage in notification server with `redis_message_client`

app/dependencies/database.py

@@ -35,13 +35,16 @@ engine = create_async_engine(
 )
 
 # Redis 连接
-redis_client = redis.from_url(settings.redis_url, decode_responses=True)
-
-# Redis 二进制数据连接 (不自动解码响应，用于存储音频等二进制数据)
-redis_binary_client = redis.from_url(settings.redis_url, decode_responses=False)
+redis_client = redis.from_url(settings.redis_url, decode_responses=True, db=0)
 
 # Redis 消息缓存连接 (db1)
-redis_message_client: redis.Redis = redis.from_url(settings.redis_url, decode_responses=True, db=1)
+redis_message_client = redis.from_url(settings.redis_url, decode_responses=True, db=1)
+
+# Redis 二进制数据连接 (不自动解码响应，用于存储音频等二进制数据，db2)
+redis_binary_client = redis.from_url(settings.redis_url, decode_responses=False, db=2)
+
+# Redis 限流连接 (db3)
+redis_rate_limit_client = redis.from_url(settings.redis_url, decode_responses=True, db=3)
 
 
 # 数据库依赖