Harden RC7 API response contracts

docs/CODEX_EXECUTION_LOG.md

@@ -10516,3 +10516,33 @@ Decision:
 
 - RC-6 is complete. RC-7 critical API response typing and OpenAPI validation
   is active.
+
+## 2026-07-18 - Belgium/North Sea RC-7 API contract hardening
+
+Implemented:
+
+- Replaced every remaining free-form successful JSON response model with a
+  concrete Pydantic schema while retaining the canonical `{"data": ...}`
+  payload shape.
+- Added reusable generic envelope, list, pagination and GeoJSON schemas plus
+  concrete project, area, assistant, YOLO preflight and QA evidence models.
+- Corrected Area serialization so persisted PostGIS geometries are converted
+  to GeoJSON before response validation.
+- Added an executable OpenAPI contract audit and focused regression tests that
+  reject missing, free-dictionary or undocumented non-envelope responses.
+- Tracked exactly eight deliberate exceptions: three health probes, four
+  persisted PNG endpoints and the streamed export download.
+
+Validation:
+
+- The API audit passed 124 implemented routes and 228 OpenAPI component
+  schemas.
+- Repository readiness passed backend compilation, 1,008 backend tests,
+  Alembic head `202607160001`, frontend typecheck and production build.
+- Offline `alembic upgrade head --sql` completed and generated 31,548 bytes of
+  migration evidence.
+
+Decision:
+
+- RC-7 is complete. RC-8 automated frontend and browser release journeys are
+  active.