Allow X-Rollbar-Access-Token header in CORS preflight response

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

Author: hauxir

app/app.py

@@ -14,7 +14,7 @@
 def add_cors_headers(response):
     response.headers["Access-Control-Allow-Origin"] = "*"
     response.headers["Access-Control-Allow-Methods"] = "POST, OPTIONS"
-    response.headers["Access-Control-Allow-Headers"] = "Content-Type"
+    response.headers["Access-Control-Allow-Headers"] = "Content-Type, X-Rollbar-Access-Token"
     return response