feat: RTL/i18n, AI translate+undo, no-refresh saves, settings perf

- RTL: force dir=rtl on LabelFilter, NotesViewToggle, LabelManagementDialog
- i18n: add missing keys (notifications, privacy, edit/preview, AI translate/undo)
- Settings pages: convert to Server Components (general, appearance) + loading skeleton
- AI menu: add Translate option (10 languages) + Undo AI button in toolbar
- Fix: saveInline uses REST API instead of Server Action → eliminates all implicit refreshes in list mode
- Fix: NotesTabsView notes sync effect preserves selected note on content changes
- Fix: auto-tag suggestions now filter already-assigned labels
- Fix: color change in card view uses local state (no refresh)
- Fix: nav links use <Link> for prefetching (Settings, Admin)
- Fix: suppress duplicate label suggestions already on note
- Route: add /api/ai/translate endpoint

keep-notes/app/(main)/settings/loading.tsx

@@ -0,0 +1,26 @@
+export default function SettingsLoading() {
+  return (
+    <div className="space-y-6 animate-pulse">
+      <div>
+        <div className="h-9 w-64 bg-muted rounded-md mb-2" />
+        <div className="h-4 w-96 bg-muted rounded-md" />
+      </div>
+      {[1, 2, 3].map((i) => (
+        <div key={i} className="rounded-lg border border-border p-6 space-y-4">
+          <div className="flex items-center gap-3">
+            <div className="h-8 w-8 bg-muted rounded-full" />
+            <div className="h-5 w-40 bg-muted rounded-md" />
+          </div>
+          <div className="h-px bg-border" />
+          <div className="flex items-center justify-between p-4 rounded-lg bg-muted/30">
+            <div className="space-y-2">
+              <div className="h-4 w-32 bg-muted rounded" />
+              <div className="h-3 w-56 bg-muted rounded" />
+            </div>
+            <div className="h-6 w-11 bg-muted rounded-full" />
+          </div>
+        </div>
+      ))}
+    </div>
+  )
+}