fix(recordings): Stop deleting the last recording from returning a 404

[brandonhs]

Summary

On the device, deleting the last recording(s) showed a "Failed to delete recording" toast even though the files were deleted. Two bugs caused this:

1. The delete routes checked if not response, so when no recordings were left ([]) they returned a 404 after the files were already deleted.
2. The 404 handler in run_release.py, which serves index.html for frontend routes, also caught API 404s and returned index.html with a 200 status. openapi-fetch then tried to parse the HTML as JSON, threw, and performDelete showed the error toast.

Changes

• run_release.py: the 404 handler now uses FastAPI's default JSON response for paths under /api/. Other paths still get index.html. This also fixes the same problem for any other API 404 on the release build.
• POST /api/recordings/bulk-delete always returns the remaining recordings, including an empty list.
• DELETE /api/recordings/{recording_path} returns a 404 only when the file does not exist (response is None).
• bulk_delete_recordings now removes deleted files from the cached self.recordings, like delete_recording already did.
• Cached durations are now cleared by full path, which is the key they are stored by. Before, they were never removed.
• delete_recording now takes recordings_lock. Both delete methods use a shared _remove_recording_file helper.
• performDelete now shows an error toast when the request returns an error status. Before, an error status showed no toast.

Fixes #554

Testing

I ran an app with the recordings router, a StaticFiles mount, and the same 404 handler as run_release.py:

Request	main	This PR
Bulk delete the last recording	200, index.html	200, []
Delete a missing recording	200, index.html	404, JSON detail
GET /recordings (frontend route)	200, index.html	200, index.html

ruff, ty, tsc and eslint pass. I have not tested this on a device.

Type of change

• Bug fix
• Feature / Refactor
• Breaking change
• Misc.

Quick Checklist

• I have reviewed my own code.
• I have tested these changes locally.
• I have tested these changes on the following platforms (optional):
  • SVC
  • microSVC (optional)
  • SVC Pro

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[brandonhs]

Forgot this still used valtio...