Silent error swallowing made it impossible to diagnose why worker
couldn't see master's heartbeat. Now logs errors from:
- updateNodeState upsert failures
- writeStateToSharedMariaDB connection/write failures
- getNodeStatesShared query failures
- list endpoint shows state count in logs
Also improved First() call to not overwrite state on error.
Bump version to v1.6.5.
In shared mode, the master may use SQLite locally while workers
write heartbeats to the shared MariaDB. The /list endpoint now
opens a temporary MariaDB connection to query node_states when
the local DB is not MariaDB.
Expose node management API endpoints for the cluster feature:
- GET /node/list — returns connected nodes with online status
- GET /node/config — returns current node + DB configuration
- POST /node/config — validates and persists node settings to x-ui.json
