feat: Memento avec dates, Markdown, reminders et auth

Tests Playwright validés ✅:
- Création de notes: OK
- Modification titre: OK
- Modification contenu: OK
- Markdown éditable avec preview: OK

Fonctionnalités:
- date-fns: dates relatives sur cards
- react-markdown + remark-gfm
- Markdown avec toggle edit/preview
- Recherche améliorée (titre/contenu/labels/checkItems)
- Reminder recurrence/location (schema)
- NextAuth.js + User/Account/Session
- userId dans Note (optionnel)
- 4 migrations créées

Ready for production + auth integration

keep-notes/package.json

@@ -5,9 +5,13 @@
   "scripts": {
     "dev": "next dev",
     "build": "next build",
-    "start": "next start"
+    "start": "next start",
+    "test": "playwright test",
+    "test:ui": "playwright test --ui",
+    "test:headed": "playwright test --headed"
   },
   "dependencies": {
+    "@auth/prisma-adapter": "^2.11.1",
     "@libsql/client": "^0.15.15",
     "@prisma/adapter-better-sqlite3": "^7.2.0",
     "@prisma/adapter-libsql": "^7.2.0",
@@ -22,15 +26,20 @@
     "better-sqlite3": "^12.5.0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "date-fns": "^4.1.0",
     "dotenv": "^17.2.3",
     "lucide-react": "^0.562.0",
     "next": "16.1.1",
+    "next-auth": "^5.0.0-beta.30",
     "prisma": "5.22.0",
     "react": "19.2.3",
     "react-dom": "19.2.3",
+    "react-markdown": "^10.1.0",
+    "remark-gfm": "^4.0.1",
     "tailwind-merge": "^3.4.0"
   },
   "devDependencies": {
+    "@playwright/test": "^1.57.0",
     "@tailwindcss/postcss": "^4",
     "@types/better-sqlite3": "^7.6.13",
     "@types/node": "^20",