feat: Standalone Speed and Cadence sensor support for Virtual Power

[SoNdA11]

Description:
To support users on traditional rollers/dumb trainers, the system must read standard Bluetooth/ANT+ speed and cadence sensors independent of a smart trainer connection.

Acceptance Criteria:

• Implement Bluetooth LE GATT profile reading for standard Cadence sensors.
• Implement Bluetooth LE GATT profile reading for standard Speed sensors.
• Create a "Virtual Power" mapping function that takes wheel speed and translates it to estimated watts based on a predefined resistance curve.
• Update the UI device pairing screen to show these sensors as separate connectable entities.