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/ui/rich-editor.tsx

@@ -15,6 +15,9 @@ type Props = {
   className?: string;
 };
 
+const mdClasses =
+  "[&_strong]:font-bold [&_em]:italic [&_code]:rounded [&_code]:bg-muted [&_code]:px-1 [&_code]:text-[0.85em] [&_h2]:text-base [&_h2]:font-bold [&_h2]:mt-3 [&_h3]:text-sm [&_h3]:font-bold [&_h3]:mt-2 [&_ul]:list-disc [&_ul]:pr-5 [&_ol]:list-decimal [&_ol]:pr-5 [&_li]:mt-0.5 [&_p]:leading-relaxed [&_p+p]:mt-2 [&_a]:underline [&_a]:text-primary";
+
 export function RichEditor({ value, onChange, placeholder, className }: Props) {
   const [tab, setTab] = useState<"edit" | "preview">("edit");
   const [preview, setPreview] = useState("");
@@ -34,7 +37,6 @@ export function RichEditor({ value, onChange, placeholder, className }: Props) {
     },
   });
 
-  // Sync external value changes (e.g. when a new lesson is loaded).
   useEffect(() => {
     if (!editor) return;
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -46,11 +48,14 @@ export function RichEditor({ value, onChange, placeholder, className }: Props) {
 
   useEffect(() => {
     if (tab !== "preview") return;
-    import("marked").then(async ({ marked }) => {
+    let cancelled = false;
+    void (async () => {
+      const { marked } = await import("marked");
       const DOMPurify = (await import("dompurify")).default;
       const html = await marked(value);
-      setPreview(DOMPurify.sanitize(html));
-    });
+      if (!cancelled) setPreview(DOMPurify.sanitize(html));
+    })();
+    return () => { cancelled = true; };
   }, [tab, value]);
 
   const ToolBtn = ({
@@ -170,13 +175,20 @@ export function RichEditor({ value, onChange, placeholder, className }: Props) {
         <EditorContent
           editor={editor}
           dir="auto"
-          className="prose prose-sm max-w-none px-3 py-2 text-sm focus-within:outline-none [&_.ProseMirror]:min-h-[80px] [&_.ProseMirror]:outline-none [&_.ProseMirror_p.is-editor-empty:first-child::before]:text-muted-foreground/50 [&_.ProseMirror_p.is-editor-empty:first-child::before]:content-[attr(data-placeholder)] [&_.ProseMirror_p.is-editor-empty:first-child::before]:float-right [&_.ProseMirror_p.is-editor-empty:first-child::before]:pointer-events-none"
+          className={cn(
+            "px-3 py-2 text-sm focus-within:outline-none",
+            mdClasses,
+            "[&_.ProseMirror]:min-h-[80px] [&_.ProseMirror]:outline-none",
+            "[&_.ProseMirror_p.is-editor-empty:first-child::before]:text-muted-foreground/50 [&_.ProseMirror_p.is-editor-empty:first-child::before]:content-[attr(data-placeholder)] [&_.ProseMirror_p.is-editor-empty:first-child::before]:float-right [&_.ProseMirror_p.is-editor-empty:first-child::before]:pointer-events-none",
+          )}
         />
       ) : (
         <div
           dir="auto"
-          className="prose prose-sm max-w-none px-3 py-2 text-sm"
-          dangerouslySetInnerHTML={{ __html: preview || "<p class='text-muted-foreground text-sm'>پیش‌نمایشی نیست.</p>" }}
+          className={cn("px-3 py-2 text-sm", mdClasses)}
+          dangerouslySetInnerHTML={{
+            __html: preview || "<p class='text-muted-foreground text-sm'>پیش‌نمایشی نیست.</p>",
+          }}
         />
       )}
     </div>