Fix Railway config: use DOCKERFILE builder, increase healthcheck timeout

- Change builder from NIXPACKS to DOCKERFILE so railway.json is respected
- Remove redundant startCommand (Dockerfile CMD handles this)
- Increase healthcheckTimeout from 100s to 300s for slower migrations

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jsb2092

questionbank/railway.json

@@ -1,13 +1,12 @@
 {
   "$schema": "https://railway.app/railway.schema.json",
   "build": {
-    "builder": "NIXPACKS"
+    "builder": "DOCKERFILE"
   },
   "deploy": {
     "numReplicas": 1,
-    "startCommand": "python manage.py migrate --noinput && gunicorn config.wsgi:application --bind 0.0.0.0:$PORT",
     "healthcheckPath": "/health/",
-    "healthcheckTimeout": 100,
+    "healthcheckTimeout": 300,
     "restartPolicyType": "ON_FAILURE",
     "restartPolicyMaxRetries": 3
   }