add: added user pages, and last messages to the home page

back/api/auth.js

@@ -31,6 +31,11 @@ router.post('/register', async (req, res) => {
         return res.status(401).send({ error: 'Username already exists' });
     }
 
+    if (!/^[a-zA-Z0-9-_]+$/.test(username)) {
+        connection.end();
+        return res.status(400).send({ error: 'Invalid username' });
+    }
+
     const hash = sha256(password);
     await addUser(connection, username, hash);
     connection.end();