Add Xbox controller diagnostics

[okch-codes]

Summary

• add Xbox/XInput detection and live input through the browser Gamepad API
• add an Xbox-specific controller diagram with sticks, triggers, D-pad, and button visualization
• integrate Xbox button diagnostics into Quick Test while excluding OS-reserved Guide and unreliable browser vibration tests
• add an Xbox Accessories handoff for permanent calibration
• improve the Xbox connection modal, cancellation, timeout, and spinner behavior
• update documentation, metadata, and automated Xbox mapping tests

Testing

• npm test
• npm run build:prod

Xbox firmware calibration remains outside the browser because the Gamepad API does not expose calibration writes.

[carpikes]

Hi, thank you for this PR! Will review it in these days and merge it.