feat: production-harden app and finalize merge-ready UX/theme baseline

- complete tokenized theme preset system and admin style guide visibility
- refine dashboard layout/scroll behavior and shared async/request UI states
- add user nav-visibility settings across API, migration, and frontend stores
- harden security headers/CSP handling and related test coverage
- enforce CI repository hygiene + frontend contract/theme/build quality gates
- update docs/env references and make migration smoke test head-aware

.github/workflows/ci.yml

@@ -90,6 +90,10 @@ jobs:
         working-directory: frontend
         run: npm install
 
+      - name: Frontend theme token policy
+        working-directory: frontend
+        run: npm run check:theme-tokens
+
       - name: Frontend typecheck
         working-directory: frontend
         run: npm run typecheck