Connect the frontend to the real GraphQL API (replace mock data)

[davidhne]

Goal

The frontend currently filters frontend/src/mocks/recipes.ts in the
browser. Wire it up to the real GraphQL backend (now live on the VM, #14)
instead, so search, filtering, sorting and paging run server-side over the
whole dataset, as the assignment requires — and pick the GraphQL
client/state management library that's still an open decision
(CLAUDE.md "Still open").

Acceptance criteria

• Pick a GraphQL client (e.g. Apollo Client, urql, graphql-request + a
  state library) and record the decision in CLAUDE.md and README
• Add it as a frontend dependency, pointed at the backend over an
  env-based URL: http://localhost:3001 in dev,
  /project2/graphql in the production build (proxied by Apache, see
  deploy/apache/project2.conf)
• HomePage's search box, RecipeFilter and sort drive the recipes
  query's search, filter, sort, limit/offset arguments —
  no client-side filtering of mock data left on the result list
• Pagination / "load more" uses the server's totalCount and
  hasMore, not just what's currently loaded in the browser
• RecipeDetailPage fetches one recipe via the recipe(id) query
  instead of reading it out of mock data
• Loading and error states: a visible loading indicator while a query
  is in flight, and a visible message (not a blank page) if a query
  fails
• The aria-live result-count announcement reads the server's
  totalCount
• frontend/src/mocks/recipes.ts and the client-side filtering in
  frontend/src/utils/recipeFilters.ts are removed once nothing
  depends on them, or kept only for tests with a comment saying so
• Component tests updated to mock the GraphQL client/network layer
  instead of importing mock data directly
• README "Current status" paragraph updated: frontend is connected to
  the API, not mock data

Notes

Backend schema (backend/src/schema.ts) already supports everything
needed — no backend changes expected: recipes(search, filter, sort, limit, offset) with RecipeFilter { categories, maxCalories, minRating },
RecipeSort (RELEVANCE/RATING/CALORIES/TITLE), recipe(id), and
categories. Builds on #16 (closed), which shipped the UI against mock
data; the live backend from #14 answers at /project2/graphql in
production.