Refactor schedule functionality in frontend

- Extract schedule logic into custom useSchedule hook
- Update BlocklistScheduleSection to use the new hook
- Add tests for useSchedule hook
- Update documentation with task progress

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/pages/BlocklistsPage.tsx

@@ -37,7 +37,7 @@ export function BlocklistsPage(): React.JSX.Element {
       )}
 
       <BlocklistSourcesSection onRunImport={handleRunImport} runImportRunning={running} />
-      <BlocklistScheduleSection onRunImport={handleRunImport} runImportRunning={running} />
+      <BlocklistScheduleSection onRunImport={handleRunImport} runImportRunning={running} importLastResult={lastResult} />
       <BlocklistImportLogSection />
 
       <ImportResultDialog