fix: mock next/font in tests and remove broken shared export

src/test/__mocks__/next-font-google.ts

@@ -0,0 +1,12 @@
+import { vi } from 'vitest';
+
+const mockFont = () => ({
+  variable: '--font-mock',
+  className: 'mock-font',
+  style: { fontFamily: 'mock-font' },
+});
+
+vi.mock('next/font/google', () => ({
+  Fraunces: mockFont,
+  Public_Sans: mockFont,
+}));