fix: remove duplicate JWT_SECRET production check (BUG-S5)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/middleware/jwt.ts

@@ -1,9 +1,6 @@
 import { createHmac, randomBytes } from 'crypto'
 import { logger } from '../lib/logger.js'
 
-if (!process.env.JWT_SECRET && process.env.NODE_ENV === 'production') {
-  throw new Error('JWT_SECRET required in production')
-}
 if (!process.env.JWT_SECRET && process.env.NODE_ENV === 'production') {
   throw new Error('JWT_SECRET required in production')
 }