Turning the files API off also stops the sweep, so expired rows stay forever #1595

Problem

files_enabled gates the five /api/v1/files routes and the lifespan worker that reclaims expired and soft-deleted files: _start_file_sweeper in main.py returns None when the flag is off.

Expired and soft-deleted are not terminal states. The sweep is the only transition out of them: it removes the bytes and then the row. So turning the flag off on a deployment that already holds rows leaves those bytes and rows unreclaimed, and nothing says so.

files_sweep_interval_sec = 0 has the same effect, and its description says cleanup is then left to the operator. The files_enabled description mentions only the endpoints.

Decision

files_enabled turns off the surface only. The routes go off, but the sweep keeps running, because the deployment still owes the deletion it promised in each file's expiry. Only files_sweep_interval_sec = 0 stops the sweep, and its description already says cleanup is then the operator's.

The name files_enabled reads as the whole capability. Rename it to say it gates the API surface, such as files_api_enabled, and accept the old name as a deprecated alias that logs once at startup.

A deployment that starts with the sweep not running and reclaimable rows present logs once that nothing will reclaim them.

Done when

• With the flag off, the routes answer as disabled and the sweep still runs.
• The flag is renamed, the old name is a deprecated alias, and the settings description says it gates the API surface only.
• A deployment holding reclaimable rows with the sweep not running says so at startup.