Improve device pairing feedback and build provenance

[lookfirst]

Summary

• gate Bluetooth pairing controls to tested Chrome and direct Chrome users to reconnect-saving guidance
• stabilize Zwift Click sleeping-controller reconnect feedback with blue pulsing controller indicators
• add a localized UTC build timestamp linked to the producing pull request
• fall back to the closed pull-request list when deployment metadata has no associated PR

Why

The Click retry loop exposed internal connection-attempt phases, causing status text, dots, and buttons to flicker while controllers slept. Unsupported browsers also exposed pairing controls that cannot work, and deployed builds lacked visible provenance.

Impact

The Devices tray now presents a stable reconnect state, unsupported browsers receive focused guidance, and every deployed footer identifies when and from which PR it was built.

Validation

• bun run ci
• 103 tests passing
• TypeScript check
• production Vite build