feat(telemetry): add unified_session telemetry to reduce detection

Implements WhatsApp's unified_session telemetry feature to reduce
detection of unofficial clients. This is an enterprise-grade implementation
inspired by whatsmeow PR #1057 and Baileys PR #2294.

Features:
- UnifiedSessionManager class with circuit breaker protection
- Server time synchronization for accurate session IDs
- Rate limiting to prevent spam (1 minute between sends)
- Prometheus metrics integration (unified_session_sent, errors)
- Structured logging for debugging
- Configurable via SocketConfig.enableUnifiedSession
- Environment variable support (BAILEYS_UNIFIED_SESSION_ENABLED)

Trigger points (matching official WhatsApp Web):
- After successful login (CB:success)
- After successful pairing (CB:iq,,pair-success)
- When sending 'available' presence

Implementation details:
- Session ID algorithm: (now + serverOffset + 3days) % 7days
- Time constants exported from Defaults/index.ts
- Full test coverage (31 tests)

References:
- https://github.com/tulir/whatsmeow/pull/1057
- https://github.com/WhiskeySockets/Baileys/pull/2294
- https://github.com/tulir/whatsmeow/issues/810

src/Utils/index.ts

@@ -36,6 +36,9 @@ export * from './cache-utils'
 export * from './circuit-breaker'
 export * from './retry-utils'
 
+// Telemetry and detection mitigation
+export * from './unified-session'
+
 // Version management
 export * from './version-cache'