feat(07-01): add quick-add HTTP handlers and route registration

- Add ListQuickAddItems, CreateQuickAddItem, UpdateQuickAddItem, DeleteQuickAddItem handler methods
- Register GET/POST /api/quick-add and PUT/DELETE /api/quick-add/{itemId} in authenticated route group
- Validate name non-empty on create and update; return 404 on update when item not found

backend/internal/api/handlers.go

@@ -636,6 +636,88 @@ func (h *Handlers) GenerateBudget(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusCreated, detail)
 }
 
+// Quick Add Item Handlers
+
+func (h *Handlers) ListQuickAddItems(w http.ResponseWriter, r *http.Request) {
+	userID := auth.UserIDFromContext(r.Context())
+	items, err := h.queries.ListQuickAddItems(r.Context(), userID)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to list quick add items")
+		return
+	}
+	writeJSON(w, http.StatusOK, items)
+}
+
+func (h *Handlers) CreateQuickAddItem(w http.ResponseWriter, r *http.Request) {
+	userID := auth.UserIDFromContext(r.Context())
+	var req struct {
+		Name string `json:"name"`
+		Icon string `json:"icon"`
+	}
+	if err := decodeJSON(r, &req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+
+	if req.Name == "" {
+		writeError(w, http.StatusBadRequest, "name is required")
+		return
+	}
+
+	item, err := h.queries.CreateQuickAddItem(r.Context(), userID, req.Name, req.Icon)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to create quick add item")
+		return
+	}
+	writeJSON(w, http.StatusCreated, item)
+}
+
+func (h *Handlers) UpdateQuickAddItem(w http.ResponseWriter, r *http.Request) {
+	userID := auth.UserIDFromContext(r.Context())
+	itemID, err := parseUUID(chi.URLParam(r, "itemId"))
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid item id")
+		return
+	}
+
+	var req struct {
+		Name      string `json:"name"`
+		Icon      string `json:"icon"`
+		SortOrder int    `json:"sort_order"`
+	}
+	if err := decodeJSON(r, &req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+
+	if req.Name == "" {
+		writeError(w, http.StatusBadRequest, "name is required")
+		return
+	}
+
+	item, err := h.queries.UpdateQuickAddItem(r.Context(), itemID, userID, req.Name, req.Icon, req.SortOrder)
+	if err != nil {
+		writeError(w, http.StatusNotFound, "quick add item not found")
+		return
+	}
+	writeJSON(w, http.StatusOK, item)
+}
+
+func (h *Handlers) DeleteQuickAddItem(w http.ResponseWriter, r *http.Request) {
+	userID := auth.UserIDFromContext(r.Context())
+	itemID, err := parseUUID(chi.URLParam(r, "itemId"))
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid item id")
+		return
+	}
+
+	if err := h.queries.DeleteQuickAddItem(r.Context(), itemID, userID); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to delete quick add item")
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
 // Settings Handlers
 
 func (h *Handlers) GetSettings(w http.ResponseWriter, r *http.Request) {