Cleanup: Automate TTS/STT folder deletion

[kartpop]

Is your feature request related to a problem?
S3 cleanup is currently separate from DB cleanup. TTS/STT folders require manual deletion as only a few projects generate real traffic, leading to potential clutter.

Describe the solution you'd like

• Identify TTS/STT voice-note storage folders eligible for deletion.
• Delete folders recursively (manual console deletion is acceptable).
• Ensure this process is separate from the DB cron/migration path.
• Verify that evaluation processes do not reuse the same folder path prior to deletion.

Original issue

Context

S3 cleanup stays separate from DB cleanup. TTS/STT folders can be deleted recursively, possibly manually via console since only ~10–12 projects have real traffic.

Acceptance criteria

• Identify TTS/STT voice-note storage folders eligible for deletion.
• Delete recursively (manual console deletion acceptable given low project count).
• Keep this work out of the DB cron/migration path.
• Confirm evals does not reuse the same folder path before deletion.