feat: implement Iteration 5 — home screen dashboard

Backend:
- internal/home: GET /home/summary endpoint
  - Today's meal plan from menu_plans/menu_items
  - Logged calories sum from meal_diary
  - Daily goal from user profile (default 2000)
  - Expiring products within 3 days
  - Last 3 saved recommendations (no AI call on home load)
- Wire homeHandler in server.go and main.go

Flutter:
- shared/models/home_summary.dart: HomeSummary, TodaySummary,
  TodayMealPlan, ExpiringSoon, HomeRecipe
- features/home/home_service.dart + home_provider.dart
- features/home/home_screen.dart: greeting, calorie progress bar,
  today's meals card, expiring banner, quick actions row,
  recommendations horizontal list

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/server/server.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/food-ai/backend/internal/auth"
 	"github.com/food-ai/backend/internal/diary"
+	"github.com/food-ai/backend/internal/home"
 	"github.com/food-ai/backend/internal/ingredient"
 	"github.com/food-ai/backend/internal/menu"
 	"github.com/food-ai/backend/internal/middleware"
@@ -29,6 +30,7 @@ func NewRouter(
 	recognitionHandler *recognition.Handler,
 	menuHandler *menu.Handler,
 	diaryHandler *diary.Handler,
+	homeHandler *home.Handler,
 	authMiddleware func(http.Handler) http.Handler,
 	allowedOrigins []string,
 ) *chi.Mux {
@@ -92,6 +94,8 @@ func NewRouter(
 			r.Delete("/{id}", diaryHandler.Delete)
 		})
 
+		r.Get("/home/summary", homeHandler.GetSummary)
+
 		r.Route("/ai", func(r chi.Router) {
 			r.Post("/recognize-receipt", recognitionHandler.RecognizeReceipt)
 			r.Post("/recognize-products", recognitionHandler.RecognizeProducts)