Implements a mechanism for GATT clients to signal their Peer ID to the server immediately after connection, allowing for robust deduplication of redundant connections.
Includes:
- New IDENTITY_CHARACTERISTIC_UUID in AppConstants
- Server-side handling of identity writes and deduplication logic
- Client-side active signaling of Peer ID upon service discovery
- Updated BluetoothConnectionTracker to map devices to Peer IDs
- Comprehensive specification document in docs/PEERID_GATT_SERVER_CLIENT_SPEC.md
