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/streamer/streamer.go

@@ -627,11 +627,11 @@ func (s *Streamer) stream(ctx context.Context) error {
 			// Peer state changes - silently ignore
 			continue
 		default:
-			s.logger.Error("Unknown message type",
+			s.logger.Warn("Unknown message type, skipping",
 				"type", msg.Type,
-				"line", string(line),
 			)
-			panic(fmt.Sprintf("Unknown RIS message type: %s", msg.Type))
+
+			continue
 		}
 
 		// Dispatch to interested handlers