feat: smart note history with manual/auto modes, delete entries, i18n fixes

- Add noteHistoryMode setting (manual default / auto) with DB migration
- Manual mode: commit button in editor toolbar creates snapshots on demand
- Auto mode: smart snapshots with 20-char diff threshold + 5min cooldown,
  structural changes (color, pin, archive, labels) bypass cooldown
- Add delete individual history entries from history modal
- Fix sidebar: Notes nav no longer active on notebook pages
- Fix sidebar icon: replace filled Lightbulb with outlined FileText
- Fix title suggestions: change from amber to sky blue color scheme
- Fix hydration mismatch: add suppressHydrationWarning on locale dates
- Complete i18n: add history, sort, and AI chat translations for all 16 languages
- Translate French AI assistant section (40+ keys) from English to French
- Update README with new features and stack info

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/components/chat/chat-sidebar.tsx

@@ -82,7 +82,7 @@ export function ChatSidebar({
                     {chat.title || t('chat.untitled')}
                   </span>
                 </div>
-                <span className="text-[10px] opacity-60 ml-6">
+                <span className="text-[10px] opacity-60 ml-6" suppressHydrationWarning>
                   {formatDistanceToNow(new Date(chat.updatedAt), { addSuffix: true, locale: dateLocale })}
                 </span>
               </div>