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- Fix sidebar: Notes nav no longer active on notebook pages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/package.json

@@ -7,7 +7,8 @@
     "build": "prisma generate && next build",
     "start": "next start",
     "db:generate": "prisma generate",
-    "db:migrate": "prisma migrate dev",
+    "db:migrate": "node scripts/safe-migrate.js",
+    "db:migrate:dev": "prisma migrate dev",
     "db:migrate:deploy": "prisma migrate deploy",
     "db:push": "prisma db push",
     "db:studio": "prisma studio",