refactor(web): unify settings panel layouts with shared toolbar/body

- Add PanelToolbar/PanelBody primitives so all four settings tabs share
  the same top-toolbar + scrollable-body rhythm under the unified header.
- API panel: drop the heavy gray shadowed TabsList; move the create
  action into the toolbar next to the tabs, lighten per-tab hints.
- Storage panel: reuse PanelToolbar for the generated-at/refresh bar.
- Account panel: wrap content in PanelBody for consistent padding.
- Models panel: keep the pinned LangBot Models (Space) card at the very
  top, above the add-custom-provider row (intentional pin), using
  PanelBody instead of a top toolbar.

web/src/app/home/components/account-settings-dialog/AccountSettingsPanel.tsx

@@ -14,6 +14,7 @@ import { httpClient } from '@/app/infra/http/HttpClient';
 import { systemInfo } from '@/app/infra/http';
 import { Loader2, ExternalLink, KeyRound, Layers } from 'lucide-react';
 import PasswordChangeDialog from '../password-change-dialog/PasswordChangeDialog';
+import { PanelBody } from '../settings-dialog/panel-layout';
 
 interface AccountSettingsPanelProps {
   // True when this panel is the active section and the dialog is open.
@@ -86,7 +87,7 @@ export default function AccountSettingsPanel({
   };
 
   return (
-    <div className="px-6 py-5">
+    <PanelBody>
       {userEmail && (
         <p className="mb-4 text-sm text-muted-foreground">{userEmail}</p>
       )}
@@ -165,6 +166,6 @@ export default function AccountSettingsPanel({
         onOpenChange={handlePasswordDialogClose}
         hasPassword={hasPassword}
       />
-    </div>
+    </PanelBody>
   );
 }