feat(room): enforce minimum room name length of 2 characters in creation and editing

server/routes/rooms.js

@@ -166,6 +166,9 @@ router.post('/', authenticateToken, async (req, res) => {
     if (!name || name.trim().length === 0) {
       return res.status(400).json({ error: 'Room name is required' });
     }
+    if (name.trim().length < 2) {
+      return res.status(400).json({ error: 'Room name must be at least 2 characters' });
+    }
 
     // M7: field length limits
     if (name.trim().length > 100) {
@@ -243,6 +246,9 @@ router.put('/:uid', authenticateToken, async (req, res) => {
     } = req.body;
 
     // M12: field length limits (same as create)
+    if (name && name.trim().length < 2) {
+      return res.status(400).json({ error: 'Room name must be at least 2 characters' });
+    }
     if (name && name.trim().length > 100) {
       return res.status(400).json({ error: 'Room name must not exceed 100 characters' });
     }