Implement RondevuAPI and RondevuSignaler classes

Added comprehensive API client and signaling implementation:

**RondevuAPI** - Single class for all Rondevu endpoints:
- Authentication: register()
- Offers: createOffers(), getOffer(), answerOffer(), getAnswer(), searchOffers()
- ICE Candidates: addIceCandidates(), getIceCandidates()
- Services: publishService(), getService(), searchServices()
- Usernames: checkUsername(), claimUsername()

**RondevuSignaler** - ICE candidate exchange:
- addIceCandidate() - Send local candidates to server
- addListener() - Poll for remote candidates (1 second intervals)
- Returns cleanup function (Binnable) to stop polling
- Handles offer expiration gracefully

**WebRTCRondevuConnection** - WebRTC connection wrapper:
- Handles offer/answer creation
- Manages ICE candidate exchange via Signaler
- Type-safe event bus for state changes and messages
- Queue and send message interfaces

**Utilities**:
- createBin() - Cleanup function collector
- Binnable type - Cleanup function signature

All classes use the shared RondevuAPI client for consistent
error handling and authentication.

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/index.ts

@@ -5,12 +5,27 @@
 
 export { ConnectionManager } from './connection-manager.js';
 export { EventBus } from './event-bus.js';
+export { RondevuAPI } from './api.js';
+export { RondevuSignaler } from './signaler.js';
+export { WebRTCRondevuConnection } from './connection.js';
+export { createBin } from './bin.js';
 
 // Export types
 export type {
-  ConnectionIdentity,
-  ConnectionState,
   ConnectionInterface,
-  Connection,
-  QueueMessageOptions
+  QueueMessageOptions,
+  Message,
+  ConnectionEvents,
+  Signaler
 } from './types.js';
+
+export type {
+  Credentials,
+  OfferRequest,
+  Offer,
+  ServiceRequest,
+  Service,
+  IceCandidate
+} from './api.js';
+
+export type { Binnable } from './bin.js';