Replace admin alerts with inline errors and toasts

frontend/src/app.tsx

@@ -16,6 +16,7 @@ export default function App() {
   const [links, setLinks] = useState<LinkItem[]>([]);
   const [page, setPage] = useState<Page>('loading');
   const [query, setQuery] = useState('');
+  const [toast, setToast] = useState<{ message: string; tone: 'success' | 'error' } | null>(null);
 
   async function refresh() {
     const current = await api.request<SetupState>('/api/me');
@@ -33,6 +34,13 @@ export default function App() {
     setLinks(await api.request<LinkItem[]>('/api/links'));
   }
 
+  function showToast(message: string, tone: 'success' | 'error' = 'success') {
+    setToast({ message, tone });
+    window.setTimeout(() => {
+      setToast((current) => (current?.message === message ? null : current));
+    }, 2500);
+  }
+
   useEffect(() => {
     refresh().catch(() => setPage('setup'));
   }, []);
@@ -67,22 +75,16 @@ export default function App() {
             onSave={async (payload, file, editingId) => {
               const fd = toFormData(payload, file);
               const url = editingId ? `/api/links/${editingId}` : '/api/links';
-              try {
-                await api.request(url, { method: editingId ? 'PATCH' : 'POST', body: fd });
-              } catch (err) {
-                const message = err instanceof Error ? err.message : String(err);
-                if (message.includes('Link name already exists')) {
-                  alert('Link names must be unique.');
-                  return;
-                }
-                throw err;
-              }
+              await api.request(url, { method: editingId ? 'PATCH' : 'POST', body: fd });
+              showToast(editingId ? 'Link updated.' : 'Link created.');
               await refresh();
             }}
             onDelete={async (id) => {
               await api.request(`/api/links/${id}`, { method: 'DELETE' });
+              showToast('Link deleted.');
               await refresh();
             }}
+            showToast={showToast}
           />
         </div>
       </Shell>
@@ -91,6 +93,7 @@ export default function App() {
 
   return (
     <Shell>
+      {toast ? <Toast message={toast.message} tone={toast.tone} /> : null}
       <Dashboard
         links={links}
         query={query}
@@ -127,6 +130,14 @@ function Shell({ children }: { children: ReactNode }) {
   return <div className="min-h-screen">{children}</div>;
 }
 
+function Toast({ message, tone }: { message: string; tone: 'success' | 'error' }) {
+  return (
+    <div className="toast-wrap" role="status" aria-live="polite">
+      <div className={`toast ${tone === 'error' ? 'toast-error' : 'toast-success'}`}>{message}</div>
+    </div>
+  );
+}
+
 function Centered({ children }: { children: ReactNode }) {
   return <div className="grid min-h-screen place-items-center p-8 text-slate-500">{children}</div>;
 }
@@ -300,15 +311,18 @@ function AdminPage({
   links,
   onSave,
   onDelete,
+  showToast,
 }: {
   links: LinkItem[];
   onSave: (payload: LinkForm, file?: File | null, editingId?: number) => Promise<void>;
   onDelete: (id: number) => Promise<void>;
+  showToast: (message: string, tone?: 'success' | 'error') => void;
 }) {
   const [form, setForm] = useState<LinkForm>(emptyForm());
   const [file, setFile] = useState<File | null>(null);
   const [editingId, setEditingId] = useState<number | null>(null);
   const [restoreText, setRestoreText] = useState('');
+  const [submitError, setSubmitError] = useState<string | null>(null);
 
   const startEdit = (link: LinkItem) => {
     setEditingId(link.id);
@@ -336,8 +350,18 @@ function AdminPage({
           className="panel space-y-2"
           onSubmit={async (event) => {
             event.preventDefault();
-            await onSave(form, file, editingId ?? undefined);
-            reset();
+            setSubmitError(null);
+            try {
+              await onSave(form, file, editingId ?? undefined);
+              reset();
+            } catch (err) {
+              const message = err instanceof Error ? err.message : String(err);
+              if (message.includes('Link name already exists')) {
+                setSubmitError('Link names must be unique.');
+                return;
+              }
+              setSubmitError(message || 'Saving failed. Please try again.');
+            }
           }}
         >
           <input className="input" value={form.name} placeholder="name" onChange={(e) => setForm({ ...form, name: e.target.value })} required />
@@ -354,6 +378,7 @@ function AdminPage({
             <button type="submit" className="btn-subtle">{editingId ? 'Update' : 'Add'}</button>
             {editingId ? <button type="button" className="btn-subtle" onClick={reset}>Cancel</button> : null}
           </div>
+          {submitError ? <p className="text-xs text-rose-400">{submitError}</p> : null}
         </form>
         <div className="panel space-y-2">
           <div className="text-xs text-slate-400">Backup / Restore</div>
@@ -396,7 +421,7 @@ function AdminPage({
               onClick={async () => {
                 const data = JSON.parse(restoreText);
                 await api.request('/api/admin/restore?dry_run=true', { method: 'POST', body: JSON.stringify({ data, confirm: false }) });
-                alert('Restore dry-run passed.');
+                showToast('Restore dry-run passed.');
               }}
             >
               Validate (dry-run)
@@ -408,7 +433,7 @@ function AdminPage({
                 if (!confirm('Apply restore now? This replaces existing users, sessions, and links.')) return;
                 const data = JSON.parse(restoreText);
                 await api.request('/api/admin/restore?dry_run=false', { method: 'POST', body: JSON.stringify({ data, confirm: true }) });
-                alert('Restore applied.');
+                showToast('Restore applied.');
                 window.location.reload();
               }}
             >