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/auth/handler.go

@@ -30,18 +30,18 @@ func (h *Handler) Login(w http.ResponseWriter, r *http.Request) {
 	r.Body = http.MaxBytesReader(w, r.Body, maxRequestBodySize)
 	var req loginRequest
 	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
-		writeErrorJSON(w, http.StatusBadRequest, "invalid request body")
+		writeErrorJSON(w, r, http.StatusBadRequest, "invalid request body")
 		return
 	}
 
 	if req.FirebaseToken == "" {
-		writeErrorJSON(w, http.StatusBadRequest, "firebase_token is required")
+		writeErrorJSON(w, r, http.StatusBadRequest, "firebase_token is required")
 		return
 	}
 
 	resp, err := h.service.Login(r.Context(), req.FirebaseToken)
 	if err != nil {
-		writeErrorJSON(w, http.StatusUnauthorized, "authentication failed")
+		writeErrorJSON(w, r, http.StatusUnauthorized, "authentication failed")
 		return
 	}
 
@@ -52,18 +52,18 @@ func (h *Handler) Refresh(w http.ResponseWriter, r *http.Request) {
 	r.Body = http.MaxBytesReader(w, r.Body, maxRequestBodySize)
 	var req refreshRequest
 	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
-		writeErrorJSON(w, http.StatusBadRequest, "invalid request body")
+		writeErrorJSON(w, r, http.StatusBadRequest, "invalid request body")
 		return
 	}
 
 	if req.RefreshToken == "" {
-		writeErrorJSON(w, http.StatusBadRequest, "refresh_token is required")
+		writeErrorJSON(w, r, http.StatusBadRequest, "refresh_token is required")
 		return
 	}
 
 	resp, err := h.service.Refresh(r.Context(), req.RefreshToken)
 	if err != nil {
-		writeErrorJSON(w, http.StatusUnauthorized, "invalid refresh token")
+		writeErrorJSON(w, r, http.StatusUnauthorized, "invalid refresh token")
 		return
 	}
 
@@ -73,12 +73,12 @@ func (h *Handler) Refresh(w http.ResponseWriter, r *http.Request) {
 func (h *Handler) Logout(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.UserIDFromCtx(r.Context())
 	if userID == "" {
-		writeErrorJSON(w, http.StatusUnauthorized, "unauthorized")
+		writeErrorJSON(w, r, http.StatusUnauthorized, "unauthorized")
 		return
 	}
 
 	if err := h.service.Logout(r.Context(), userID); err != nil {
-		writeErrorJSON(w, http.StatusInternalServerError, "logout failed")
+		writeErrorJSON(w, r, http.StatusInternalServerError, "logout failed")
 		return
 	}
 
@@ -86,14 +86,18 @@ func (h *Handler) Logout(w http.ResponseWriter, r *http.Request) {
 }
 
 type errorResponse struct {
-	Error string `json:"error"`
+	Error     string `json:"error"`
+	RequestID string `json:"request_id,omitempty"`
 }
 
-func writeErrorJSON(w http.ResponseWriter, status int, msg string) {
+func writeErrorJSON(w http.ResponseWriter, r *http.Request, status int, msg string) {
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(status)
-	if err := json.NewEncoder(w).Encode(errorResponse{Error: msg}); err != nil {
-		slog.Error("failed to write error response", "err", err)
+	if encodeErr := json.NewEncoder(w).Encode(errorResponse{
+		Error:     msg,
+		RequestID: middleware.RequestIDFromCtx(r.Context()),
+	}); encodeErr != nil {
+		slog.ErrorContext(r.Context(), "failed to write error response", "err", encodeErr)
 	}
 }