Backfill Eps Endpoint

Backfill EPS actuals from AlphaVantage EARNINGS into earnings_dates.

Unblocks the PEAD (post-earnings-announcement-drift) signal in the probability engine. Idempotent — re-running only fills new gaps.

Budget ~14 min per 1,000 symbols at the default throttle. The queue read used to truncate at 1,000, which is where the old "~800 symbols" estimate came from; the real depth was 8,053 on 2026-09-02. The response now reports symbols_matching (the whole queue) next to symbols_processed, so pass a limit and work it down across passes rather than expecting one to finish.