Add Velocity calculation logic and GUI toggle (end-to-end MVP).

[M1DNYT3]

This PR completes velocity transmission end-to-end, adding RPC settings and a GUI toggle on top of the foundation from #1754.

What's added:

• Protobuf velocity transmission via ProtobufBridge, per-tracker
• RPC settings support - toggle persists across restarts
• GUI toggle in General Settings with i18n

Toggle's GUI Path:
Settings > General > Tracker Settings > Toggle is at the very bottom of the section.

Technicalities:
Most of the line count (~400) comes from regenerated ProtobufMessages.java. The handwritten change itself is small.

Depends on SlimeVR/SolarXR-Protocol#202, should be merged only after the submodule is updated to the tracked HEAD.

Addresses the issue: #25

[M1DNYT3]

Force pushes in history are changes made by spotless.
For some reason, one application wasn't enough for it to fix all the issues in Tracker.kt, so I had to push it twice, and I didn't want to make 2 separate commits for spotless alone.

[M1DNYT3]

At some point, I had a conversation with @ButterscotchV in DMs, and there was a recommendation expressed to ship the whole feature (Implying a toggle, nothing overkill) in one PR.

The description is edited accordingly to reflect each affected part of the code.
The handwritten part (meaning not regenerated flatbuf, and not regenerated ProtobufMessages) follows the existing code architecture 1:1 and reuses the methods, styles, and classes, where necessary.