714e8efb3d
Add max_connections config (default 256) with -m/--max-connections CLI flag. Server wraps on_client in asyncio.Semaphore to prevent fd exhaustion under load. Value reloads on SIGHUP; active connections drain normally. Also adds pool_size/pool_max_idle config fields and first_hop_pool wiring in server.py (used by next commits), and fixes asyncio.TimeoutError -> TimeoutError lint warnings.