Refactor blocklist import registration to async startup flow

Docs/Tasks.md

@@ -69,6 +69,7 @@ Reference: `Docs/Refactoring.md` for full analysis of each issue.
    - Issue: `blocklist_import.register` uses `asyncio.get_event_loop().run_until_complete` then falls back to `asyncio.ensure_future`, which is fragile and can fail if the application is already running inside an event loop.
    - Propose: Refactor blocklist job registration to use a pure async bootstrap flow invoked from the lifespan handler, or resolve schedule configuration before starting the scheduler instead of forcing synchronous loop execution.
    - Test: Add tests validating blocklist job registration in both non-running and running event loop contexts, and verify the registration path does not raise loop state errors.
+   - Status: completed
 
 10. Standardize async offloading and thread-backed sync work behind a shared executor abstraction
    - Goal: Remove scattered `asyncio.get_event_loop().run_in_executor` / `asyncio.ensure_future` patterns and give the backend a single, consistent way to run blocking file, CPU-bound, or compatibility work.