fix: remove intentional exception in /ping endpoint to prevent 500 errors

[plural-copilot]

Summary:
This PR removes the deliberately thrown exception in the /ping endpoint that caused about one-third of requests to fail with 500 Internal Server Errors. This fix ensures that the endpoint always returns a successful response.

Changes Made:

• Removed the if int(time.time()) % 3 == 0: raise Exception("unknown internal error") block from the /ping handler in app/main.py.

Rationale:
The intentional exception was likely introduced for testing but is causing elevated error rates in production, triggering alerts and disrupting health checks. This change restores reliable behavior of the /ping endpoint without modifying other functionality.

After merging, rebuild and redeploy the container for the flow-test service in the boot-prod cluster to resolve the alert and prevent further unnecessary failures.