iPhone 11 Boot Loop and Failure to Power On After iOS 18.4.1 Update

I own an iPhone 11 that encountered a severe issue after updating to iOS 18.4.1. Post-update, the device began crashing frequently, then restarted and failed to power on. It now remains completely unresponsive.

When attempting Recovery Mode, the Apple logo appears briefly but disappears, and the device does not boot or stay powered on. I have tried the following:

1. Recovery Mode: Connected to a computer with the latest iTunes/Finder, but the device shuts down before Update or Restore can complete.

2. Charging: Used an original Apple charger for over 30 minutes, but the issue persists.

Additional details:

- The update process was not interrupted (no internet or power issues).

- No physical damage (drops, water exposure) or unauthorized repairs.

- Backup status: I have/do not have a recent iCloud/computer backup.

The device is now unusable, and I suspect an iOS 18.4.1 bug or a hardware issue triggered by the update. Please advise on further steps or if a repair is necessary.

Thank you for your support.