Extract base classes MdnsEmulator and BluetoothEmulator

[Copilot]

Refactor emulator implementations to eliminate code duplication by extracting common logic into abstract base classes.

Changes

Created MdnsEmulator base class

• TCP server lifecycle (bind, listen, close)
• mDNS service registration/unregistration
• Network interface discovery
• Socket write operations and hex/byte conversion utilities

Created BluetoothEmulator base class

• BLE peripheral manager lifecycle
• Connection state management and event subscriptions
• Android permission handling
• Service/characteristic management and advertisement

Refactored 5 emulator classes

• FtmsMdnsEmulator → extends MdnsEmulator
• OpenBikeControlMdnsEmulator → extends MdnsEmulator
• ZwiftEmulator → extends BluetoothEmulator
• OpenBikeControlBluetoothEmulator → extends BluetoothEmulator
• RemotePairing → extends BluetoothEmulator

Example

Before:

class FtmsMdnsEmulator extends TrainerConnection {
  ServerSocket? _tcpServer;
  Registration? _mdnsRegistration;
  
  Future<InternetAddress?> _findLocalIP() async {
    final interfaces = await NetworkInterface.list();
    // ... 15 lines of interface discovery
  }
  
  Future<void> _createTcpServer() async {
    _tcpServer = await ServerSocket.bind(/* ... */);
    // ... 10 lines of server setup
  }
}

After:

class FtmsMdnsEmulator extends MdnsEmulator {
  @override
  Future<void> startServer() async {
    final localIP = await findLocalIP();  // Inherited
    await createTcpServer(36867);         // Inherited
    await registerMdnsService(/* ... */); // Inherited
  }
}

Impact

• ~293 lines of duplicate code eliminated
• Fixed missing await keywords in async notification calls
• Consistent patterns across all emulator types

Original prompt

use a base class "MdnsEmulator" for FtmsMdnsEmulator and OpenBikeControlMdnsEmulator, and put the shared logic to that base class

do the same with ZwiftEmulator and OpenBikeControlBluetoothEmulator and RemotePairing in a base class "BluetoothEmulator"

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