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

frontend/src/features/settings/index.ts

@@ -4,6 +4,7 @@ export interface UserSettings {
   auto_run_enabled: boolean;
   run_interval_minutes: number;
   request_delay_seconds: number;
+  nav_visible_pages: string[];
 }
 
 export interface ChangePasswordPayload {