Add frontend API client and TanStack Query hooks

Install @tanstack/react-query, create a fetch-based API client with typed
functions for all endpoints, and add query/mutation hooks for games, pokemon,
runs, and encounters. Includes Vite dev proxy for /api and QueryClientProvider
setup.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/hooks/usePokemon.ts

@@ -0,0 +1,10 @@
+import { useQuery } from '@tanstack/react-query'
+import { getPokemon } from '../api/pokemon'
+
+export function usePokemon(id: number | null) {
+  return useQuery({
+    queryKey: ['pokemon', id],
+    queryFn: () => getPokemon(id!),
+    enabled: id !== null,
+  })
+}