Turn on crash detection

Crash detection is an optional helper that watches for the kind of sudden motion a collision causes and offers to start a report for you.

To turn it on:
1. Open the Accident Assistant (/me/accident).
2. Use the Crash detection toggle on the start screen.

What it does, honestly:
- It's a best-effort convenience that can prompt you to start a report after a possible crash.
- It is NOT a certified safety device and does not call for help on its own. In a real emergency, always use Call 911 yourself.

You can turn it off any time from the same toggle. With it off, you simply start a report by hand whenever you need one.