Simplify connected-speaker setup and stage USB firmware updates

[eirabie]

Summary

USB-connected speakers currently show several competing actions. Simplify /install/ with one main settings action, a firmware status row and expandable Wi-Fi/password recovery. Missing credentials put repair first; detected pending USB updates take priority. Fresh installation retains explicit erase confirmation, and post-install Back returns to recovery.

Add a separate signed, application-only USB updater for firmware supporting the new protocol. It preserves credentials, prayer settings, playback history and recordings, with the previous application retained for startup rollback. Download timeouts restore recovery controls, and uncertain transfers require reconnection and a status check. Verified updates show the power handoff even if USB cleanup fails, with credential recovery guidance where needed. USB updates remain disabled (usbUpdateEnabled: false) pending physical qualification and publication of a capable release. Automatic release adoption cannot enable them.

Area

• Homepage or public documentation
• Hardware/build guidance
• Browser installer
• Project or deployment configuration

Validation

• Relevant routes and links were checked
• User-facing behavior was tested in applicable browsers and viewport sizes
• Accessibility impact was reviewed
• No firmware is compiled by this repository

Automated and browser checks

• Node 24.19.0: formatting, Astro/TypeScript checks and 176 unit tests passed.
• Chromium, desktop WebKit and narrow WebKit: 357 development-browser checks passed (3 built-only checks skipped), plus 171 built-site checks. Coverage includes keyboard access, failure/recovery paths and update handoff.
• Release import and static build verified the selected published v0.4.0 artifacts and 9 pages, with the simulator excluded.
• Website CI passed on 794d385.

Physical qualification

Validation for this PR is automated/browser-only. Physical USB transfer, data preservation, power handoff, rollback and runtime qualification remain required before activation; see the qualification requirements. Verified writing and boot selection do not establish successful startup.

Licensing and privacy

• No new third-party media or dependency licensing concerns
• No new collection or transmission of user data
• Any licensing, attribution, or privacy impact is documented