fix: enhance security by blocking plugins with dangerous JS patterns and enforcing strict session secret length

lib/auth/crypto.ts

@@ -5,9 +5,17 @@ const ALGORITHM = 'aes-256-gcm';
 const IV_LENGTH = 12;
 const TAG_LENGTH = 16;
 
+const MIN_SECRET_LENGTH = 32;
+
 function getKey(): Buffer {
   const secret = process.env.SESSION_SECRET;
   if (!secret) throw new Error('SESSION_SECRET not configured');
+  if (secret.length < MIN_SECRET_LENGTH) {
+    throw new Error(
+      `SESSION_SECRET must be at least ${MIN_SECRET_LENGTH} characters (got ${secret.length}). ` +
+      `Generate one with: node -e "console.log(require('crypto').randomBytes(32).toString('hex'))"`
+    );
+  }
   return createHash('sha256').update(secret).digest();
 }