Move prefixes table maintenance from DBHandler to PrefixHandler

- DBHandler now only maintains asns and asn_peerings tables
- PrefixHandler maintains both prefixes and live_routes tables
- This consolidates all prefix-related operations in one handler

internal/routewatch/prefixhandler.go

@@ -168,7 +168,7 @@ func (h *PrefixHandler) flushBatchLocked() {
 
 	// Apply updates to database
 	for _, update := range prefixMap {
-		// Get or create prefix
+		// Get or create prefix (this maintains the prefixes table)
 		prefix, err := h.db.GetOrCreatePrefix(update.prefix, update.timestamp)
 		if err != nil {
 			h.logger.Error("Failed to get/create prefix",