72% of EKB quarters (1735/2408) have broken micro-precision geom in
cad_quarters_geom. NSPD returns valid quarter polygon in CAT_QUARTER_STATS
(36381) feature but Phase 4 was only consuming stats.
Add upsert_quarter_geom_from_feature: CTE-based UPDATE that transforms
3857 polygon to 4326 and writes only when existing geom is NULL or broken
(bbox width outside 100-10000m), verified via SQL-side sanity check.
Wire into Phase 4 with begin_nested savepoint: malformed NSPD GeoJSON
(self-intersecting ring) rollbacks only geom UPDATE, preserves
upsert_quarter_stats.
Closes part of #168 (follow-up data quality fix for #179).
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