fix: prevent stale camera playback errors and stream restart races

[Timverhoogt]

Summary

• Bind playback promises to the current session, stream, and generation so Stop/privacy cannot be overwritten by late callbacks.
• Ignore duplicate stream announcements and reject callbacks from old connections.
• Keep Stop available while playback starts; distinguish interruption from autoplay denial.
• Advance the PWA cache and asset queries to v72 with synchronized test expectations.

Verification

• Chromium camera suite: 12 passed, including deferred playback completion/cancellation, old-session callbacks, duplicate stream notifications, and genuine autoplay denial.
• Targeted Python camera, PWA, motor UI, announcement, HA bridge, and Kids tests passed locally.
• Exact patched camera, index, and service-worker bytes verified over HTTPS on the owner-approved live dashboard; rollback backup retained.
• No camera activation, speech, movement, or runtime restart was performed. Physical camera acceptance remains owner-supervised.

Deployment note

This narrowly scoped static dashboard hotfix was already applied with owner approval. This PR preserves the same fix in the source repository.