feat(#263 sub-A): cad_* overlay schemas + cadastre territorial_zones (ПЗЗ)
Phase 1 (migration 101): создаёт 5 новых таблиц cad_territorial_zones,
cad_red_lines, cad_engineering_structures, cad_risk_zones,
cad_opportunity_parcels. Idempotent (IF NOT EXISTS), GIST-индексы.
Phase 2 partial (ПЗЗ only):
- NSPDBulkClient.get_features_in_bbox_grid — async grid-walk WMS GetFeatureInfo
- NSPDBulkClient.get_territorial_zones_in_bbox — convenience wrapper layer 875838
- harvest_quarter Phase 2.5 — вызов get_territorial_zones_in_bbox после grid-walk
- _save_territorial_zones — UPSERT loop с SAVEPOINT per-row, ON CONFLICT zone_id
9 unit tests (mock DB): insert/upsert/no-geom/no-id/error-isolation/savepoint pattern.
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