fix(ci): split unit/integration tests and fix landing test failures

- Separate unit tests (fast, no system deps) from integration test
  shards to prevent vi.mock db leakage across test types
- Fix hero test: update expected subtitle to match current copy
- Fix FAQ test: add missing json-ld alias in vitest config and mock
- Integration tests run in 4 parallel shards (30min timeout each)

tests/unit/landing/components.test.tsx

@@ -41,7 +41,7 @@ describe("Hero", () => {
 
   it("renders the subheadline", () => {
     render(<Hero />);
-    expect(screen.getByText("Every image tool you need.")).toBeDefined();
+    expect(screen.getByText(/free, open-source image toolkit/)).toBeDefined();
   });
 
   it("renders the CTA button linking to GitHub", () => {