scrape_cadastre.py previously incremented requests_count only by
grid_walk_requests, so snapshot-only quarters (and the entire ekb_full
job after PR #179 skips grid-walk on broken geom) reported 0 NSPD
requests — misleading for observability.
Add HarvestResult.snapshot_requests counter (Phase 1 search + Phase 1.5
per-cat probes) and a total_requests property. Update Celery task to
write total_requests into cadastre_jobs.requests_count.
Tests added for the new property + Phase 1 snapshot_requests=1 assertion.