Add startsWith parameter to getTopics method

Added optional startsWith parameter to topics query:
- Filters topics by prefix on the server side
- Updated TypeScript types
- Supports response with startsWith field

Version bumped to 0.7.5

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@xtr-dev/rondevu-client",
-  "version": "0.7.4",
+  "version": "0.7.5",
   "description": "TypeScript client for Rondevu topic-based peer discovery and signaling server",
   "type": "module",
   "main": "dist/index.js",