Add production hardening: health check, streamer panic fix, db maintenance

- Add health check endpoint at /.well-known/healthcheck.json that
  verifies database and RIS Live connectivity, returns 200/503

- Fix panic in streamer when encountering unknown RIS message types
  by logging a warning and continuing instead of crashing

- Add DBMaintainer for periodic database maintenance:
  - VACUUM every 6 hours to reclaim space
  - ANALYZE every hour to update query statistics
  - Graceful shutdown support

- Add Vacuum() and Analyze() methods to database interface

internal/routewatch/app.go

@@ -44,6 +44,7 @@ type RouteWatch struct {
 	prefixHandler  *PrefixHandler
 	peeringHandler *PeeringHandler
 	asnFetcher     *ASNFetcher
+	dbMaintainer   *DBMaintainer
 }
 
 // New creates a new RouteWatch instance
@@ -115,6 +116,10 @@ func (rw *RouteWatch) Run(ctx context.Context) error {
 	rw.asnFetcher.Start()
 	rw.server.SetASNFetcher(rw.asnFetcher)
 
+	// Start database maintenance goroutine
+	rw.dbMaintainer = NewDBMaintainer(rw.db, rw.logger.Logger)
+	rw.dbMaintainer.Start()
+
 	// Wait for context cancellation
 	<-ctx.Done()
 
@@ -155,6 +160,11 @@ func (rw *RouteWatch) Shutdown() {
 		rw.asnFetcher.Stop()
 	}
 
+	// Stop database maintainer
+	if rw.dbMaintainer != nil {
+		rw.dbMaintainer.Stop()
+	}
+
 	// Stop services
 	rw.streamer.Stop()