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/lib/note-preview.ts

@@ -0,0 +1,33 @@
+/**
+ * Plain-text preview for list view (light markdown stripping).
+ */
+export function stripMarkdownPreview(raw: string, maxLen = 180): string {
+  if (!raw?.trim()) return ''
+  let t = raw
+    .replace(/^#{1,6}\s+/gm, '')
+    .replace(/```[\s\S]*?```/g, ' ')
+    .replace(/\*\*([^*]+)\*\*/g, '$1')
+    .replace(/\*([^*]+)\*/g, '$1')
+    .replace(/`([^`]+)`/g, '$1')
+    .replace(/\[(.+?)]\([^)]+\)/g, '$1')
+    .replace(/^\s*[-*+]\s+/gm, '')
+    .replace(/^\s*\d+\.\s+/gm, '')
+    .replace(/\n+/g, ' ')
+    .replace(/\s+/g, ' ')
+    .trim()
+  if (t.length > maxLen) {
+    return `${t.slice(0, maxLen).trim()}…`
+  }
+  return t
+}
+
+export function getNoteDisplayTitle(note: { title: string | null; content: string; type: string }, untitled: string): string {
+  const title = note.title?.trim()
+  if (title) return title
+  if (note.type === 'checklist') {
+    const line = note.content?.split('\n').find((l) => l.trim())
+    if (line) return stripMarkdownPreview(line, 80) || untitled
+  }
+  const preview = stripMarkdownPreview(note.content || '', 100)
+  return preview || untitled
+}