feat(FN-2456): persist task token usage on task records

- Add schema v44 migration to persist task-level token usage totals and first/last usage timestamps on tasks
- Extend core task types, store create/update flows, and exports to round-trip token usage data
- Add migration and TaskStore regression tests for token usage persistence, null clearing, and reinitialization behavior
- Update dashboard async handling and tests to prevent post-unmount state updates and reduce flaky assertion timing

packages/dashboard/app/components/__tests__/QuickEntryBox.test.tsx

@@ -1185,7 +1185,9 @@ describe("QuickEntryBox", () => {
       });
 
       // After creation, input is cleared and focus is restored
-      expect((textarea as HTMLTextAreaElement).value).toBe("");
+      await waitFor(() => {
+        expect((textarea as HTMLTextAreaElement).value).toBe("");
+      });
 
       // With autoExpand=true (default), textarea auto-expands on focus restore
       // but disclosure resets to collapsed — controls hidden until user toggles again