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/dish/handler.go

@@ -7,6 +7,7 @@ import (
 	"strconv"
 
 	"github.com/go-chi/chi/v5"
+	"github.com/food-ai/backend/internal/infra/middleware"
 )
 
 // Handler handles HTTP requests for dishes.
@@ -34,8 +35,8 @@ func (h *Handler) Search(w http.ResponseWriter, r *http.Request) {
 	}
 	results, searchError := h.repo.Search(r.Context(), query, limit)
 	if searchError != nil {
-		slog.Error("search dishes", "err", searchError)
-		writeError(w, http.StatusInternalServerError, "failed to search dishes")
+		slog.ErrorContext(r.Context(), "search dishes", "err", searchError)
+		writeError(w, r, http.StatusInternalServerError, "failed to search dishes")
 		return
 	}
 	if results == nil {
@@ -48,8 +49,8 @@ func (h *Handler) Search(w http.ResponseWriter, r *http.Request) {
 func (h *Handler) List(w http.ResponseWriter, r *http.Request) {
 	dishes, err := h.repo.List(r.Context())
 	if err != nil {
-		slog.Error("list dishes", "err", err)
-		writeError(w, http.StatusInternalServerError, "failed to list dishes")
+		slog.ErrorContext(r.Context(), "list dishes", "err", err)
+		writeError(w, r, http.StatusInternalServerError, "failed to list dishes")
 		return
 	}
 	if dishes == nil {
@@ -63,12 +64,12 @@ func (h *Handler) GetByID(w http.ResponseWriter, r *http.Request) {
 	id := chi.URLParam(r, "id")
 	dish, err := h.repo.GetByID(r.Context(), id)
 	if err != nil {
-		slog.Error("get dish", "id", id, "err", err)
-		writeError(w, http.StatusInternalServerError, "failed to get dish")
+		slog.ErrorContext(r.Context(), "get dish", "id", id, "err", err)
+		writeError(w, r, http.StatusInternalServerError, "failed to get dish")
 		return
 	}
 	if dish == nil {
-		writeError(w, http.StatusNotFound, "dish not found")
+		writeError(w, r, http.StatusNotFound, "dish not found")
 		return
 	}
 	writeJSON(w, http.StatusOK, dish)
@@ -77,13 +78,17 @@ func (h *Handler) GetByID(w http.ResponseWriter, r *http.Request) {
 // --- helpers ---
 
 type errorResponse struct {
-	Error string `json:"error"`
+	Error     string `json:"error"`
+	RequestID string `json:"request_id,omitempty"`
 }
 
-func writeError(w http.ResponseWriter, status int, msg string) {
+func writeError(w http.ResponseWriter, r *http.Request, status int, msg string) {
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(status)
-	_ = json.NewEncoder(w).Encode(errorResponse{Error: msg})
+	_ = json.NewEncoder(w).Encode(errorResponse{
+		Error:     msg,
+		RequestID: middleware.RequestIDFromCtx(r.Context()),
+	})
 }
 
 func writeJSON(w http.ResponseWriter, status int, v any) {

backend/internal/domain/dish/repository.go

@@ -312,13 +312,20 @@ func (r *Repository) Create(ctx context.Context, req CreateRequest) (recipeID st
 		return "", fmt.Errorf("insert dish: %w", err)
 	}
 
-	// Insert tags.
+	// Insert tags — upsert into tags first so the FK constraint is satisfied
+	// even when the AI generates a tag slug that does not exist yet.
 	for _, slug := range req.Tags {
-		if _, err := tx.Exec(ctx,
+		if _, upsertErr := tx.Exec(ctx,
+			`INSERT INTO tags (slug, name) VALUES ($1, $2) ON CONFLICT (slug) DO NOTHING`,
+			slug, slug,
+		); upsertErr != nil {
+			return "", fmt.Errorf("upsert tag %s: %w", slug, upsertErr)
+		}
+		if _, insertErr := tx.Exec(ctx,
 			`INSERT INTO dish_tags (dish_id, tag_slug) VALUES ($1, $2) ON CONFLICT DO NOTHING`,
 			dishID, slug,
-		); err != nil {
-			return "", fmt.Errorf("insert dish tag %s: %w", slug, err)
+		); insertErr != nil {
+			return "", fmt.Errorf("insert dish tag %s: %w", slug, insertErr)
 		}
 	}