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/components/header.tsx

@@ -330,12 +330,12 @@ export function Header({
         <div className="flex flex-1 justify-end gap-4 items-center">
 
           {/* Settings Button */}
-          <button
-            onClick={() => router.push('/settings')}
+          <Link
+            href="/settings"
             className="flex items-center justify-center size-10 rounded-full hover:bg-slate-100 dark:hover:bg-slate-800 text-slate-600 dark:text-slate-300 transition-colors"
           >
             <Settings className="w-5 h-5" />
-          </button>
+          </Link>
 
           {/* User Avatar Menu */}
           <DropdownMenu>
@@ -356,13 +356,17 @@ export function Header({
                   {currentUser?.email && <p className="w-[200px] truncate text-sm text-muted-foreground">{currentUser.email}</p>}
                 </div>
               </div>
-              <DropdownMenuItem onClick={() => router.push('/settings/profile')} className="cursor-pointer">
-                <User className="mr-2 h-4 w-4" />
-                <span>{t('settings.profile') || 'Profile'}</span>
+              <DropdownMenuItem asChild className="cursor-pointer">
+                <Link href="/settings/profile">
+                  <User className="mr-2 h-4 w-4" />
+                  <span>{t('settings.profile') || 'Profile'}</span>
+                </Link>
               </DropdownMenuItem>
-              <DropdownMenuItem onClick={() => router.push('/admin')} className="cursor-pointer">
-                <Shield className="mr-2 h-4 w-4" />
-                <span>{t('nav.adminDashboard')}</span>
+              <DropdownMenuItem asChild className="cursor-pointer">
+                <Link href="/admin">
+                  <Shield className="mr-2 h-4 w-4" />
+                  <span>{t('nav.adminDashboard')}</span>
+                </Link>
               </DropdownMenuItem>
               <DropdownMenuItem onClick={() => signOut()} className="cursor-pointer text-red-600 focus:text-red-600">
                 <LogOut className="mr-2 h-4 w-4" />