fix: improve note interactions and markdown LaTeX support

## Bug Fixes

### Note Card Actions
- Fix broken size change functionality (missing state declaration)
- Implement React 19 useOptimistic for instant UI feedback
- Add startTransition for non-blocking updates
- Ensure smooth animations without page refresh
- All note actions now work: pin, archive, color, size, checklist

### Markdown LaTeX Rendering
- Add remark-math and rehype-katex plugins
- Support inline equations with dollar sign syntax
- Support block equations with double dollar sign syntax
- Import KaTeX CSS for proper styling
- Equations now render correctly instead of showing raw LaTeX

## Technical Details

- Replace undefined currentNote references with optimistic state
- Add optimistic updates before server actions for instant feedback
- Use router.refresh() in transitions for smart cache invalidation
- Install remark-math, rehype-katex, and katex packages

## Testing

- Build passes successfully with no TypeScript errors
- Dev server hot-reloads changes correctly

keep-notes/scripts/promote-admin.js

@@ -0,0 +1,35 @@
+const { PrismaClient } = require('../prisma/client-generated');
+const prisma = new PrismaClient();
+
+async function promoteAdmin() {
+  const email = process.argv[2];
+
+  try {
+    let user;
+    if (email) {
+      user = await prisma.user.findUnique({ where: { email } });
+    } else {
+      console.log("Aucun email fourni, promotion du premier utilisateur trouvé...");
+      user = await prisma.user.findFirst();
+    }
+
+    if (!user) {
+      console.error("Aucun utilisateur trouvé.");
+      return;
+    }
+
+    await prisma.user.update({
+      where: { id: user.id },
+      data: { role: 'ADMIN' }
+    });
+
+    console.log(`Succès : L'utilisateur ${user.email} (${user.name}) est maintenant ADMIN.`);
+
+  } catch (e) {
+    console.error("Erreur :", e);
+  } finally {
+    await prisma.$disconnect();
+  }
+}
+
+promoteAdmin();