Feature/create faqs endpoint

[james-cross]

• Added /api/faqs route with a dedicated getFaqs helper and full unit test.
• Supports optional location query param to filter FAQs by LocationKey.
• Created fetch-client-groups.js script to output client-groups.json from DB.
• Refactored existing /api/categories and /api/locations routes:
  • Extracted DB logic to getCategories and getLocations helpers.
  • Added or updated unit tests for each helper with robust DB mocks.
  • Ensured proper TypeScript type safety by declaring collection generics.
• Standardised pattern for API routes: minimal route.ts with reusable pure helper for easy test coverage.
• Verified all helper unit tests pass and type check cleanly.