fix: fix menu generation errors and show planned meals on home screen

Backend fixes:
- migration 003: add 'menu' value to recipe_source enum (was causing SQLSTATE 22P02)
- migration 004: rename recipe_products→recipe_ingredients, product_id→ingredient_id (was causing SQLSTATE 42P01)
- dish/repository.go: fix INSERT INTO tags using $1/$1 for two columns → $1/$2 (was causing SQLSTATE 42P08)
- home/handler.go: replace non-existent saved_recipes table with correct joins (recipes→dishes→dish_translations, user_saved_recipes) so today's plan and recommendations load correctly
- reqlog: new slog.Handler wrapper that adds request_id and stack trace to ERROR-level logs
- all handlers: slog.Error→slog.ErrorContext so error logs include request context; writeError includes request_id in response body

Client:
- home_screen.dart: extend home screen to future dates, show planned meals as ghost entries
- l10n: add new localisation keys for home screen date navigation and planned meal UI

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

backend/cmd/server/main.go

@@ -13,12 +13,14 @@ import (
 	"github.com/food-ai/backend/internal/infra/config"
 	"github.com/food-ai/backend/internal/infra/database"
 	"github.com/food-ai/backend/internal/infra/locale"
+	"github.com/food-ai/backend/internal/infra/reqlog"
 )
 
 func main() {
-	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
+	baseHandler := slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
 		Level: slog.LevelInfo,
-	}))
+	})
+	logger := slog.New(reqlog.New(baseHandler))
 	slog.SetDefault(logger)
 
 	if runError := run(); runError != nil {