semantic-curation: fix anchors, metadata, and relations across backend + specs

- Replace legacy @PURPOSE with @BRIEF across 241 files
- Add missing [C:N] complexity tiers to function contracts in core modules
- Fix tombstone contracts: add @STATUS DEPRECATED to 5 deprecated anchors
- Resolve 7 unresolved @RELATION edges in executor.py (DictionaryManager, TranslationPreview, etc.)
- Fix flat hierarchical IDs in 4 test files (22 test functions)
- Fix invalid tags/relations in logger.py (@ADR, @CONSEQUENCES, DISABLED_BY)
- Rebuild semantic index: 9,576 contracts, 4,742 edges, 0 parse warnings

backend/src/app.py

@@ -1434,7 +1434,7 @@ if frontend_path.exists():
     app.mount("/_app", StaticFiles(directory=str(frontend_path / "_app")), name="static")
 
     # #region App.AppModule.ServeSpa [TYPE Function] [C:1]
-    # @PURPOSE Serves the SPA frontend for any path not matched by API routes.
+    # @BRIEF Serves the SPA frontend for any path not matched by API routes.
     # @PRE frontend_path exists.
     # @POST Returns the requested file or index.html.
     @app.get("/{file_path:path}", include_in_schema=False)
@@ -1454,7 +1454,7 @@ if frontend_path.exists():
     # #endregion App.AppModule.ServeSpa
 else:
     # #region App.AppModule.ReadRoot [TYPE Function] [C:1]
-    # @PURPOSE A simple root endpoint to confirm that the API is running when frontend is missing.
+    # @BRIEF A simple root endpoint to confirm that the API is running when frontend is missing.
     # @PRE None.
     # @POST Returns a JSON message indicating API status.
     @app.get("/")