feat: add getConnectedDevice method and update TypeScript definitions

[mateusdegobi]

Problem

Error using the BluetoothManager.getConnectedDevice method

Fix

• Created the getConnectedDevice method
• Added the missing native methods:
• • unpair(address: string) — unpairs a device
• • isDeviceConnected() — returns a boolean
• • getConnectedDeviceAddress() — returns the address as a string
• • getConnectedDevice() — now works, returns { name, address } or null
• • Event constants (EVENT_DEVICE_FOUND, EVENT_CONNECTION_LOST, etc.)