Add startsWith filter to topics endpoint

Added optional startsWith parameter to GET /topics endpoint:
- Filters topics by prefix using SQL LIKE operator
- Updated storage interface and implementations (SQLite & D1)
- Added query param documentation
- Returns startsWith in response when used

Version bumped to 0.1.1

🤖 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-server",
-  "version": "0.1.0",
+  "version": "0.1.1",
   "description": "Topic-based peer discovery and signaling server for distributed P2P applications",
   "main": "dist/index.js",
   "scripts": {