test: the gate's output carries no noise to hide a real warning in

- Home tests mocked the api without downloadIndex, so every card's download button logged a
  missing-queryFn error (64 stderr blocks per run).
- QueryState rendered without an i18n instance; Modal.fullscreen awaited a synchronous act,
  which React reports as an act environment it does not support.
- pytest: Starlette 1.x's TestClient is built on httpx2 and warned on every run without it
  (pinned in requirements-dev); alembic.ini declares its path separator.

frontend/src/components/Home.dom.test.tsx

@@ -49,6 +49,7 @@ vi.mock("../lib/api", () => ({
     setState: () => Promise.resolve(),
     watchLaterAdd: () => Promise.resolve(),
     watchLaterRemove: () => Promise.resolve(),
+    downloadIndex: () => Promise.resolve({}), // the cards' download buttons read it
   },
   DISCOVER_BUDGETS: ["short", "medium", "long", "any"],
   discoverCardKey: (c: { source: string; id: string }) => `${c.source}:${c.id}`,