USB bridge: host input devices simulated USB/HID/serial endpoints

[Kinin-Code-Offical]

Goal: Allow mapping a PC mouse/controller to a simulated USB device endpoint that firmware can read.

Notes:

• For Arduino Uno-class boards, this may be constrained; document supported boards and fallback via serial.

Acceptance:

• A clear API and routing exists; can be disabled when unused.

[github-actions]

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