9970780e7a
aiomqtt/paho exception strings can include the broker URI with embedded credentials (mqtt://user:pass@host) or auth detail. The 502 response from /import and the message field on /test-connection echoed these verbatim via str(exc). - Add _sanitize_mqtt_error() that maps known patterns (auth, refused, DNS, TLS, timeout) to coarse, credential-free categories - Original exception still logged at WARNING level for operator debug - Drop hostname:port from TimeoutError messages - /test-connection unexpected-error path no longer interpolates exc Tests: 6 new (auth/refused/DNS/TLS/unknown sanitization, end-to-end fetch_networkmap leak check).