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/components/note-card.tsx

@@ -20,10 +20,14 @@ import {
   Pin,
   Tag,
   Trash2,
+  Bell,
 } from 'lucide-react'
 import { useState } from 'react'
 import { deleteNote, toggleArchive, togglePin, updateColor, updateNote } from '@/app/actions/notes'
 import { cn } from '@/lib/utils'
+import { formatDistanceToNow } from 'date-fns'
+import { fr } from 'date-fns/locale'
+import { MarkdownContent } from './markdown-content'
 
 interface NoteCardProps {
   note: Note
@@ -105,6 +109,16 @@ export function NoteCard({ note, onEdit, onDragStart, onDragEnd, onDragOver, isD
         <Pin className="absolute top-3 right-3 h-4 w-4 text-gray-600 dark:text-gray-400" fill="currentColor" />
       )}
 
+      {/* Reminder Icon */}
+      {note.reminder && new Date(note.reminder) > new Date() && (
+        <Bell 
+          className={cn(
+            "absolute h-4 w-4 text-blue-600 dark:text-blue-400",
+            note.isPinned ? "top-3 right-9" : "top-3 right-3"
+          )} 
+        />
+      )}
+
       {/* Title */}
       {note.title && (
         <h3 className="text-base font-medium mb-2 pr-6 text-gray-900 dark:text-gray-100">
@@ -173,9 +187,15 @@ export function NoteCard({ note, onEdit, onDragStart, onDragEnd, onDragOver, isD
 
       {/* Content */}
       {note.type === 'text' ? (
-        <p className="text-sm text-gray-700 dark:text-gray-300 whitespace-pre-wrap line-clamp-10">
-          {note.content}
-        </p>
+        note.isMarkdown ? (
+          <div className="text-sm line-clamp-10">
+            <MarkdownContent content={note.content} />
+          </div>
+        ) : (
+          <p className="text-sm text-gray-700 dark:text-gray-300 whitespace-pre-wrap line-clamp-10">
+            {note.content}
+          </p>
+        )
       ) : (
         <div className="space-y-1">
           {note.checkItems?.map((item) => (
@@ -217,6 +237,11 @@ export function NoteCard({ note, onEdit, onDragStart, onDragEnd, onDragOver, isD
         </div>
       )}
 
+      {/* Creation Date */}
+      <div className="mt-2 text-xs text-gray-500 dark:text-gray-400">
+        {formatDistanceToNow(new Date(note.createdAt), { addSuffix: true, locale: fr })}
+      </div>
+
       {/* Action Bar - Shows on Hover */}
       <div
         className="absolute bottom-0 left-0 right-0 p-2 flex items-center justify-end gap-1 opacity-0 group-hover:opacity-100 transition-opacity"