feat: add optimistic concurrency guards for draft editor, pricing and publish flows

add optimistic concurrency guards via expected scheme version id

protect draft editor, pricing snapshot, remap and publish flows from stale mutations
protect version creation from stale current version state

keep backward compatibility with optional query guards

verify 409 conflict behavior for stale clients and 200 for valid flows

backend/docs/api-map.md

@@ -20,6 +20,7 @@
 - GET /api/v1/schemes/{scheme_id}/current
 - GET /api/v1/schemes/{scheme_id}/versions
 - POST /api/v1/schemes/{scheme_id}/versions
+- GET /api/v1/schemes/{scheme_id}/publish/validation
 - POST /api/v1/schemes/{scheme_id}/publish
 - POST /api/v1/schemes/{scheme_id}/unpublish
 - POST /api/v1/schemes/{scheme_id}/rollback
@@ -47,3 +48,22 @@
 
 ## app/api/routes/audit.py
 - GET /api/v1/schemes/{scheme_id}/audit
+
+## app/api/routes/publish.py
+- POST /api/v1/schemes/{scheme_id}/draft/pricing/snapshot
+- GET /api/v1/schemes/{scheme_id}/draft/publish-preview
+- POST /api/v1/schemes/{scheme_id}/draft/remap/preview
+- POST /api/v1/schemes/{scheme_id}/draft/remap/apply
+
+## app/api/routes/admin.py
+- GET /api/v1/admin/schemes/{scheme_id}/current/artifacts
+- GET /api/v1/admin/schemes/{scheme_id}/current/validation
+- POST /api/v1/admin/schemes/{scheme_id}/current/display/regenerate
+- POST /api/v1/admin/display/backfill
+- GET /api/v1/admin/artifacts/publish-preview/audit
+- POST /api/v1/admin/artifacts/publish-preview/cleanup
+
+## Notes
+- This file is an operational route index, not a generated OpenAPI export.
+- Update this map in the same change set when adding, removing, renaming, or moving routes.
+- Editor routes are maintained separately and should be synced from current source before relying on this file as a full route inventory.