Integrate secret parameter into peer classes

- Add secret field to PeerOptions interface
- Pass secret when creating offers in CreatingOfferState
- Pass secret when answering offers in AnsweringState
- Bump version to 0.7.7

🤖 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": "0.7.6",
+  "version": "0.7.7",
   "description": "TypeScript client for Rondevu topic-based peer discovery and signaling server",
   "type": "module",
   "main": "dist/index.js",