Refactor app helpers and use AppStateDep in config router

Move service-dependent helper wrappers from app.utils to app.helpers and update config router activation/rollback to use explicit AppState dependency.

Docs/Tasks.md

@@ -17,7 +17,7 @@ Reference: `Docs/Refactoring.md` for full analysis of each issue.
   - Fix: replace direct `request.app.state.settings` access with `SettingsDep` or other explicit dependencies such as `ServerStatusDep` and `PendingRecoveryDep` in router function signatures.
   - Expected outcome: routers become easier to unit test, composition is more explicit, and shared state access is only available through documented FastAPI dependencies.
 
-- Several utility modules under `backend/app/utils/` import service layer code (`app.services.*`). Utilities should remain low-level helpers and not depend on higher-level service logic.
+- Status: **done** — Several utility modules under `backend/app/utils/` import service layer code (`app.services.*`). Utilities should remain low-level helpers and not depend on higher-level service logic.
   - Fix: move service-dependent helpers into `app/services/` or extract shared logic into a new `app/helpers/` layer, keeping `app/utils/` purely independent.
   - Expected outcome: lower coupling between utility and service layers, cleaner dependency direction, and better maintainability.