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)/layout.tsx

@@ -24,7 +24,7 @@ export default async function MainLayout({
           <Sidebar className="w-64 flex-none flex-col bg-white dark:bg-[#1e2128] border-r border-slate-200 dark:border-slate-800 overflow-y-auto hidden md:flex" user={session?.user} />
 
           {/* Main Content Area */}
-          <main className="flex-1 overflow-y-auto bg-background-light dark:bg-background-dark p-4 scroll-smooth">
+          <main className="flex min-h-0 flex-1 flex-col overflow-y-auto bg-background-light dark:bg-background-dark p-4 scroll-smooth">
             {children}
           </main>
         </div>