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/internal/domain/userproduct/handler.go

@@ -35,8 +35,8 @@ func (handler *Handler) List(responseWriter http.ResponseWriter, request *http.R
 	userID := middleware.UserIDFromCtx(request.Context())
 	userProducts, listError := handler.repo.List(request.Context(), userID)
 	if listError != nil {
-		slog.Error("list user products", "user_id", userID, "err", listError)
-		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to list user products")
+		slog.ErrorContext(request.Context(), "list user products", "user_id", userID, "err", listError)
+		writeErrorJSON(responseWriter, request, http.StatusInternalServerError, "failed to list user products")
 		return
 	}
 	if userProducts == nil {
@@ -50,18 +50,18 @@ func (handler *Handler) Create(responseWriter http.ResponseWriter, request *http
 	userID := middleware.UserIDFromCtx(request.Context())
 	var req CreateRequest
 	if decodeError := json.NewDecoder(request.Body).Decode(&req); decodeError != nil {
-		writeErrorJSON(responseWriter, http.StatusBadRequest, "invalid request body")
+		writeErrorJSON(responseWriter, request, http.StatusBadRequest, "invalid request body")
 		return
 	}
 	if req.Name == "" {
-		writeErrorJSON(responseWriter, http.StatusBadRequest, "name is required")
+		writeErrorJSON(responseWriter, request, http.StatusBadRequest, "name is required")
 		return
 	}
 
 	userProduct, createError := handler.repo.Create(request.Context(), userID, req)
 	if createError != nil {
-		slog.Error("create user product", "user_id", userID, "err", createError)
-		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to create user product")
+		slog.ErrorContext(request.Context(), "create user product", "user_id", userID, "err", createError)
+		writeErrorJSON(responseWriter, request, http.StatusInternalServerError, "failed to create user product")
 		return
 	}
 	writeJSON(responseWriter, http.StatusCreated, userProduct)
@@ -72,7 +72,7 @@ func (handler *Handler) BatchCreate(responseWriter http.ResponseWriter, request
 	userID := middleware.UserIDFromCtx(request.Context())
 	var items []CreateRequest
 	if decodeError := json.NewDecoder(request.Body).Decode(&items); decodeError != nil {
-		writeErrorJSON(responseWriter, http.StatusBadRequest, "invalid request body")
+		writeErrorJSON(responseWriter, request, http.StatusBadRequest, "invalid request body")
 		return
 	}
 	if len(items) == 0 {
@@ -82,8 +82,8 @@ func (handler *Handler) BatchCreate(responseWriter http.ResponseWriter, request
 
 	userProducts, batchError := handler.repo.BatchCreate(request.Context(), userID, items)
 	if batchError != nil {
-		slog.Error("batch create user products", "user_id", userID, "err", batchError)
-		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to create user products")
+		slog.ErrorContext(request.Context(), "batch create user products", "user_id", userID, "err", batchError)
+		writeErrorJSON(responseWriter, request, http.StatusInternalServerError, "failed to create user products")
 		return
 	}
 	writeJSON(responseWriter, http.StatusCreated, userProducts)
@@ -96,18 +96,18 @@ func (handler *Handler) Update(responseWriter http.ResponseWriter, request *http
 
 	var req UpdateRequest
 	if decodeError := json.NewDecoder(request.Body).Decode(&req); decodeError != nil {
-		writeErrorJSON(responseWriter, http.StatusBadRequest, "invalid request body")
+		writeErrorJSON(responseWriter, request, http.StatusBadRequest, "invalid request body")
 		return
 	}
 
 	userProduct, updateError := handler.repo.Update(request.Context(), id, userID, req)
 	if errors.Is(updateError, ErrNotFound) {
-		writeErrorJSON(responseWriter, http.StatusNotFound, "user product not found")
+		writeErrorJSON(responseWriter, request, http.StatusNotFound, "user product not found")
 		return
 	}
 	if updateError != nil {
-		slog.Error("update user product", "id", id, "err", updateError)
-		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to update user product")
+		slog.ErrorContext(request.Context(), "update user product", "id", id, "err", updateError)
+		writeErrorJSON(responseWriter, request, http.StatusInternalServerError, "failed to update user product")
 		return
 	}
 	writeJSON(responseWriter, http.StatusOK, userProduct)
@@ -120,24 +120,28 @@ func (handler *Handler) Delete(responseWriter http.ResponseWriter, request *http
 
 	if deleteError := handler.repo.Delete(request.Context(), id, userID); deleteError != nil {
 		if errors.Is(deleteError, ErrNotFound) {
-			writeErrorJSON(responseWriter, http.StatusNotFound, "user product not found")
+			writeErrorJSON(responseWriter, request, http.StatusNotFound, "user product not found")
 			return
 		}
-		slog.Error("delete user product", "id", id, "err", deleteError)
-		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to delete user product")
+		slog.ErrorContext(request.Context(), "delete user product", "id", id, "err", deleteError)
+		writeErrorJSON(responseWriter, request, http.StatusInternalServerError, "failed to delete user product")
 		return
 	}
 	responseWriter.WriteHeader(http.StatusNoContent)
 }
 
 type errorResponse struct {
-	Error string `json:"error"`
+	Error     string `json:"error"`
+	RequestID string `json:"request_id,omitempty"`
 }
 
-func writeErrorJSON(responseWriter http.ResponseWriter, status int, msg string) {
+func writeErrorJSON(responseWriter http.ResponseWriter, request *http.Request, status int, msg string) {
 	responseWriter.Header().Set("Content-Type", "application/json")
 	responseWriter.WriteHeader(status)
-	_ = json.NewEncoder(responseWriter).Encode(errorResponse{Error: msg})
+	_ = json.NewEncoder(responseWriter).Encode(errorResponse{
+		Error:     msg,
+		RequestID: middleware.RequestIDFromCtx(request.Context()),
+	})
 }
 
 func writeJSON(responseWriter http.ResponseWriter, status int, value any) {