iPhone 13 does not turn on

I have an iPhone 13 (bought new in April 2024), IOS version 25 or 26 (I'm not sure), and last I checked it had around 83% battery capacity. It was at around 30% battery and was plugged into a charger while I was actively using it when the screen suddenly went completely black with no warning. There was a thin red line on the bottom of my screen before my phone completely turned off.

Since then:

• No Apple logo appears.
• Force restart doesn't do anything.
• Screen stays completely black.
• No vibration, sounds, or signs of life.
• Calling the phone goes straight to "unreachable."
• Windows doesn't seem to detect the iPhone.
• No drops or water damage.

One thing I noticed the day before: while using the phone on the same charger, it showed that it was charging, but the battery percentage was still decreasing instead of increasing. (But I quickly fixed this and changed my charging port!).

Has anyone seen this before? Does this sound like a battery issue, charging IC/power-management issue, logic board failure, or something else?