feat(wizard): cache مشخصه globally instead of per topic/category/brand

The specs combobox drew only from materials in the selected topic, further
narrowed by the row's category and brand, so a spec was offered only when
some material in that topic shared the same category AND brand. On a new
quote the user therefore lost specs recorded in earlier quotes.

- api.specsList(): new global source reading the attribute-definitions
  registry (topic/category/brand independent)
- materialOptions('spec'): unions the registry, specs of all materials,
  and specs typed in sibling rows — no topic/category/brand filter
- EditModal: same global registry added to its spec options

Verified the registry endpoint returns labels and that the union includes
specs absent from material attributes (e.g. 'مسی').

frontend/src/lib/api.ts

@@ -1218,6 +1218,17 @@ export const api = {
   brandsList: async (): Promise<{ id: string; name: string }[]> => {
     return getData<{ id: string; name: string }[]>(`/brands?page_size=${PAGE_SIZE}`);
   },
+  // مشخصه‌ها — رجیستری سراسری (attribute-definitions)، مستقل از تاپیک/دسته/برند.
+  // ویزارد از این لیست به‌عنوان منبع سراسری مشخصه‌ها استفاده می‌کند تا مشخصه‌های
+  // ثبت‌شده در پیشنهادهای قبلی همیشه در دسترس باشند.
+  specsList: async (): Promise<string[]> => {
+    const raw = await getData<{ label?: string; attribute_key?: string }[]>(
+      `/attribute-definitions?page_size=${PAGE_SIZE}`,
+    );
+    return raw
+      .map((d) => (d.label || "").trim() || (d.attribute_key || "").replace(/^spec_/, "").trim())
+      .filter(Boolean);
+  },
 
   // ---------- واحدها (از بک‌اند) ----------
   unitsList: async (): Promise<RawUnit[]> => {