Add admin-only case reset functionality

Introduce a new "reset" action for bulk operations and a dedicated
endpoint for individual case resets. These features allow administrators
to revert a case to its raw audio state by deleting derived artifacts
like transcripts, analysis input, and documents. The functionality also
includes renaming `.m4a.failed` files back to `.m4a` to re-trigger
transcription.

This commit also:
- Adds a `reset_case_artefacts` helper function to `case_actions.rs`.
- Implements the `handle_reset_case` endpoint.
- Adds the "Reset" button to the UI for administrators.
- Includes unit and integration tests to verify the new functionality
  and access control.

whisper/docker-compose.yml

@@ -3,7 +3,7 @@ services:
     image: doctate-whisper:latest
     container_name: doctate-whisper
     environment:
-      - WHISPER_MODEL=large-v3-turbo
+      - WHISPER_MODEL=large-v3
       - WHISPER_COMPUTE_TYPE=float16
       - NVIDIA_VISIBLE_DEVICES=all
       - NVIDIA_DRIVER_CAPABILITIES=compute,utility