Fix signature validation bug for serviceFqn with colons

The validateServicePublish function was incorrectly parsing the signature
message when serviceFqn contained colons (e.g., 'chat:2.0.0@user').

Old logic: Split by ':' and expected exactly 4 parts
Problem: serviceFqn 'chat:2.0.0@user' contains a colon, so we get 5 parts

Fixed:
- Allow parts.length >= 4
- Extract timestamp from the last part
- Reconstruct serviceFqn from all middle parts (parts[2] to parts[length-2])

This fixes the '403 Invalid signature for username' error that was
preventing service publication.

package.json

@@ -22,6 +22,7 @@
   "dependencies": {
     "@hono/node-server": "^1.19.6",
     "@noble/ed25519": "^3.0.0",
+    "@xtr-dev/rondevu-client": "^0.13.0",
     "better-sqlite3": "^12.4.1",
     "hono": "^4.10.4"
   }