Cron Reload Screener Cache

Re-read screener_cache into this process's in-memory _screener_rows.

Exists for the out-of-process batch (app/scripts/run_screener_batch_job.py, 2026-08-07 batch isolation). When the batch runs in its own Railway container it commits rows to Postgres but cannot mutate the WEB process's memory, which is what the authenticated /api/screener path serves from. It calls this afterwards to close that gap.

Synchronous on purpose — the caller wants to know whether the reload landed, and load_screener_cache() already carries its own 3x retry + backoff. Safe to call any time; it is exactly what the in-process batch path does at cron.py:655. Auth: X-Cron-Secret.