feat(dashboard): drop the category filter

The category filter is not used: remove it end to end — the toolbar's category
combobox (desktop + mobile drawer), its option list, the active-filter count and
the filterQuotes() clause it drove, plus the now-unused `category` field in the
Filters type. Supplier and status filters are unchanged.

The backend's own quote filtering by category is untouched (it filters on the
quote's supplier category when ?category_id= is passed), so the API keeps its
contract; only the dashboard UI stops offering the filter.

frontend/src/lib/quoteUtils.ts

@@ -336,9 +336,8 @@ export function termsheetSummary(store: Store, q: Quote): { title: string; sub:
 // فیلترهای دفتر
 export function filterQuotes(
   store: Store,
-  filters: { category: string; supplier: string; status: string; search: string },
+  filters: { supplier: string; status: string; search: string },
 ): Quote[] {
-  const catVal = filters.category.trim();
   const supVal = filters.supplier.trim();
   const stVal = filters.status.trim();
   const q = filters.search.trim().toLowerCase();
@@ -361,10 +360,6 @@ export function filterQuotes(
     if (stKey && quote.status !== stKey) return false;
 
     const matInfo = activeItems(quote).map((li) => materialById(store.materials, li.material_id));
-    // v2.7: دسته روی تأمین‌کننده است و بک‌اند هم پیشنهادها را با دسته‌ی
-    // تأمین‌کننده فیلتر می‌کند — همین قاعده اینجا هم اعمال می‌شود تا لیست و
-    // فیلتر یک رفتار داشته باشند.
-    if (catVal && !(supObj.categories || []).includes(catVal)) return false;
 
     if (q) {
       const hay =