feat: implement frontend Web UI pages

- Add types for all API models (MealPlan, Recipe, Ingredient, etc.)
- Add API client with mealPlannerApi wrapper for all endpoints
- Implement Dashboard with weekly meal plan grid view
- Implement Pantry page with add/remove functionality
- Implement MealDetail page with recipe display
- Implement ShoppingList page with aisle grouping
- Add ShoppingList route to App.tsx
- Add vite-env.d.ts for Vite env type support

frontend/src/vite-env.d.ts

@@ -0,0 +1,9 @@
+/// <reference types="vite/client" />
+
+interface ImportMetaEnv {
+  readonly VITE_API_URL?: string
+}
+
+interface ImportMeta {
+  readonly env: ImportMetaEnv
+}