Add comprehensive logging with tracing, file rotation, and systemd integration

- Add tracing-appender and tracing-journald for production logging
- Add LoggingConfig with trace_sample_rate, json_output, journald options
- Expand init_logging() with file rotation, journald, and stderr layers
- Add sanitize_path() helper for PII protection in logs
- Instrument FUSE operations with #[instrument] and trace decision points
- Instrument gRPC handlers (10 methods) with span correlation
- Add spawn instrumentation for health monitor, indexer, watcher tasks
- Add broadcast lag handling (RecvError::Lagged) in event subscribers
- Fix webhook.rs expect() calls with proper error handling
- Add logging to patterns.rs, collections.rs, artwork.rs database ops
- Add Drop impl logging for PluginManager and WatchHandle
- Update systemd service with rate limiting and journal output
- Add logrotate config and example config.toml with logging section

musicfs/dist/musicfs.service

@@ -11,10 +11,17 @@ RestartSec=5
 User=musicfs
 Group=musicfs
 
+Environment="RUST_LOG=musicfs=info,warn"
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=musicfs
+RateLimitIntervalSec=30s
+RateLimitBurst=1000
+
 NoNewPrivileges=true
 ProtectSystem=strict
 ProtectHome=read-only
-ReadWritePaths=/var/cache/musicfs /mnt/music
+ReadWritePaths=/var/cache/musicfs /var/log/musicfs /mnt/music
 PrivateTmp=true
 
 [Install]