- Remove SseClientService and ConnectionMode.sseClient
- Add ConnectionMode.tcp with MeshCoreTcpService (port 5000)
- NetworkScannerService: scan TCP port 5000 via raw Socket.connect
- mDNS service type changed to _meshcore._tcp
- connection_dialog: connect via connectTcp() instead of connectToSseServer()
- home_screen: show WiFi icon and label for TCP mode
- Bump meshcore_client to pick up TCP transport support
Move BLE communication layer (command queue, frame parser/builder,
protocol constants, data models) into a standalone reusable Dart package
at ../meshcore_client. App model files become thin re-export wrappers,
keeping all existing consumers working without import changes.