chore: update favicons to match tempo-web

Replaced pixelated favicons with higher quality versions from tempo-web.
The .ico file is now 14KB (was 5KB) with better resolution.

Dark/light variants preserved correctly:
- favicon-dark = light icon for dark mode
- favicon-light = dark icon for light mode

Amp-Thread-ID: https://ampcode.com/threads/T-019bfffa-f34c-771c-82e9-b35a2fb14058
Co-authored-by: Amp <amp@ampcode.com>

Author: gakonst