Add backend API contract audit

docs/API_CONTRACTS.md

@@ -161,6 +161,16 @@ Backend responsibilities:
 - Calculate area in square meters using projected CRS.
 - Store bbox.
 
+### GET `/api/v1/projects/{project_id}/areas/{area_id}`
+
+Returns one project area. The payload uses the same `AreaRead` shape as the
+area list endpoint and includes persisted GeoJSON geometry for map display.
+
+### PATCH `/api/v1/projects/{project_id}/areas/{area_id}`
+
+Updates the area name and/or geometry. Geometry updates follow the same
+validation, repair and metric-calculation rules as area creation.
+
 ## Datasets
 
 ### POST `/api/v1/projects/{project_id}/datasets/upload`
@@ -339,7 +349,7 @@ Apply buffer distance to vector features.
 
 Intersect source vector dataset with another vector dataset.
 
-### POST `/api/v1/projects/{project_id}/datasets/{dataset_id}/vector/stats`
+### GET `/api/v1/projects/{project_id}/datasets/{dataset_id}/vector/stats`
 
 Return vector stats (feature counts and geometry summary).
 
@@ -347,6 +357,12 @@ Return vector stats (feature counts and geometry summary).
 
 Return vector bounds and feature count.
 
+### GET `/api/v1/projects/{project_id}/datasets/{dataset_id}/content`
+
+Returns stored vector dataset content through the canonical API envelope.
+Vector content is returned as GeoJSON/JSON payload data. Raster content is not
+served through this endpoint.
+
 ## Jobs
 
 ### POST `/api/v1/projects/{project_id}/jobs`
@@ -670,11 +686,12 @@ Response persists a `quality_check` and `metrics` rows through the existing QA/Q
 
 If the reference dataset has no persisted vector features, the endpoint returns `REFERENCE_FEATURES_NOT_FOUND`. It does not calculate fake QA metrics.
 
-### POST `/api/v1/analysis/building-stats`
+#### Future analysis route: `/api/v1/analysis/building-stats`
 
-Input: area + vector building layer.
+Not implemented in the active API surface. Future input is expected to combine
+an area with a vector building layer.
 
-### POST `/api/v1/analysis/object-detection`
+#### Future analysis route: `/api/v1/analysis/object-detection`
 
 Request:
 
@@ -693,7 +710,7 @@ Request:
 
 Response: `AnalysisRunRead`.
 
-### POST `/api/v1/analysis/segmentation`
+#### Future analysis route: `/api/v1/analysis/segmentation`
 
 Same pattern as object detection, but output includes masks and polygonized geometries.
 
@@ -1027,7 +1044,7 @@ intentionally does not use the JSON envelope because it is a browser/file-downlo
 path; callers that need canonical API JSON should use `/content` for JSON/GeoJSON
 artifacts.
 
-### POST `/api/v1/exports/yolo`
+#### Future export route: `/api/v1/exports/yolo`
 
 Export annotations/detections to YOLO format.