URGENT: Ship /api/v1/utilities/{slug}/geometry + fix /territories/{slug}/geometry slug matching

Fixes Relay map-loading bug (Victor 21:06 UTC). Relay requests /api/v1/territories/vermont-electric-cooperative/geometry and 404s. Root cause: (1) /territories/{slug}/geometry matches against territories.id (territory row id), not regions.slug or utility slug — nobody would discover that shape. (2) Relay reasonably assumed utility-slug → geometry works. Ship primary fix: GET /api/v1/utilities/{slug}/geometry joining utilities → regions (eia_id, SERVICE_TERRITORY type) → territories. Secondary fix: make /api/v1/territories/{slug}/geometry accept regions.slug as well as territories.id (backward compatible). Add VEC canary regression test (expects 200 once geometry backfill runs — skip or mock until then). Update OpenAPI. Cache: public, s-maxage=86400, stale-while-revalidate=86400.