fix: quality audit — memory leaks, dead prose classes, stale state scope

- safe-markdown: add `cancelled` flag to async useEffect; no more
  setState after unmount when component is destroyed mid-import
- rich-editor: same cleanup for preview tab effect; also remove dead
  `prose prose-sm max-w-none` classes (Tailwind Typography not installed)
  and replace with explicit arbitrary-selector markdown styling that
  actually renders using existing design tokens
- profile-certificate-slot: drop dead `ORDER_LABEL`, `order` variable,
  and `physicalOrder` from `MineCertificateResponse`; physical orders
  are disabled — these were leftover references causing lint noise
- learning-panel: change `issuingCert: boolean` → `issuingCertFor:
  number | null` so only the targeted user's button shows a spinner;
  a boolean shared across all users caused the wrong row to animate
  when the admin switched selected users mid-request

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/admin/learning-panel.tsx

@@ -65,7 +65,7 @@ export function LearningPanel() {
   const [sort, setSort] = useState<SortKey>("xp");
   const [selectedId, setSelectedId] = useState<number | null>(null);
   const [unlocking, setUnlocking] = useState(false);
-  const [issuingCert, setIssuingCert] = useState(false);
+  const [issuingCertFor, setIssuingCertFor] = useState<number | null>(null);
   const [page, setPage] = useState(1);
 
   useEffect(() => {
@@ -117,7 +117,7 @@ export function LearningPanel() {
   };
 
   const issueCertificate = async (id: number) => {
-    setIssuingCert(true);
+    setIssuingCertFor(id);
     try {
       await http.post(`/api/admin/users/${id}/certificate/issue`, {});
       toast.success("گواهینامه با موفقیت صادر شد");
@@ -125,7 +125,7 @@ export function LearningPanel() {
     } catch (e) {
       toast.error(toUserError(e, "صدور گواهینامه ممکن نشد"));
     } finally {
-      setIssuingCert(false);
+      setIssuingCertFor(null);
     }
   };
 
@@ -393,11 +393,15 @@ export function LearningPanel() {
                     <Button
                       size="sm"
                       variant="default"
-                      disabled={issuingCert}
+                      disabled={issuingCertFor === detailQ.data.learning.user.id}
                       onClick={() => issueCertificate(detailQ.data!.learning.user.id)}
                       className="gap-1.5"
                     >
-                      {issuingCert ? <Loader2 className="h-3.5 w-3.5 animate-spin" /> : <Award className="h-3.5 w-3.5" />}
+                      {issuingCertFor === detailQ.data.learning.user.id ? (
+                        <Loader2 className="h-3.5 w-3.5 animate-spin" />
+                      ) : (
+                        <Award className="h-3.5 w-3.5" />
+                      )}
                       صدور گواهینامه
                     </Button>
                   </div>