Pool sensor v2: VCC monitoring, database resilience, receiver improvements

- Added voltage monitoring table and storage pipeline
- Extended pool payload to 17 bytes with VCC field (protocol v2)
- Improved database connection pool resilience (reduced pool size, aggressive recycling, pool disposal on failure)
- Added environment variable support for database configuration
- Fixed receiver MQTT deprecation warning (CallbackAPIVersion.VERSION2)
- Silenced excessive RSSI status logging in receiver
- Added reset flag tracking and reporting
- Updated Docker compose with DB config and log rotation limits

docker-compose.dev.yml

@@ -17,10 +17,10 @@ services:
       - SSH_KEY_PATH=/workspace/.ssh/id_rsa
       - STALL_WINDOW_SECONDS=${STALL_WINDOW_SECONDS:-300}
       - RESTART_COOLDOWN_SECONDS=${RESTART_COOLDOWN_SECONDS:-3600}
-      # DB override for dev testing; defaults to an invalid host to simulate DB-down
-      - DB_HOST=${DB_HOST:-invalid-host}
+      # DB config for dev; connect to real database
+      - DB_HOST=${DB_HOST:-192.168.43.102}
       - DB_PORT=${DB_PORT:-3306}
       - DB_USER=${DB_USER:-weatherdata}
-      - DB_PASSWORD=${DB_PASSWORD:-cfCU$swM!HfK82%*}
+      - DB_PASSWORD=${DB_PASSWORD:-cfCUswMHfK82!}
       - DB_NAME=${DB_NAME:-weatherdata}
       - DB_CONNECT_TIMEOUT=${DB_CONNECT_TIMEOUT:-5}