cab71e6a26
This commit introduces a new startup cleanup routine for the Doctate client. The cleanup process reaps stale markers and orphaned audio files to adhere to data minimization principles and maintain client efficiency. Specifically, it performs the following actions: - Removes markers that are older than 72 hours and have been confirmed by the server. This ensures that old, irrelevant metadata is purged. - Cleans up orphaned audio files (e.g., `.m4a` without corresponding `.meta.json` or vice-versa) that are older than 24 hours. This prevents the accumulation of audio data that will never be uploaded, as such files are silently ignored by the uploader. - Removes any temporary files (`.tmp`) left over from interrupted writes, as these are considered invalid at startup. The `filetime` crate is added as a dependency to facilitate setting modification times for testing purposes.