Document the v0.5.0 release and Waveshare qualification

[eirabie]

Summary

The README and engineering guides still describe v0.5.0 as unpublished. Update them for the released Atom and Waveshare Box V2 builds, sync the public release notes, and add a dated qualification report.

The report separates completed installation, signed OTA, recovery and powered RTC RESET checks from untested battery retention, RTC-only scheduled playback and browser USB updates. Earlier preparation measurements remain dated historical evidence.

Hardware impact

• No new required hardware
• Adds optional hardware
• Changes the required reference BOM

Standalone impact

Clarifies the existing standalone behavior, initial internet time synchronization and Waveshare powered RTC restart support. Changes are limited to Markdown documentation.

Testing

• Automated documentation checks: whitespace, 101 relative links/anchors, public release-note wording, production image sizes and source/evidence consistency passed. Final diff reviewed after rebasing onto current main.
• Hardware evidence: documents completed attended Waveshare installation, isolated signed OTA/interruption/rollback, production restoration and public descriptor checks; reuses dated listening, BOOT and RTC evidence within their tested scope. Records the installer reconnect fallback and remaining validation limits.

Licensing/media

• No new third-party media or dependency licensing concerns
• Licensing/attribution details are documented in this PR

Retains the release audio attribution and permissions link.