monorepo projects do not resolve nested app favicons

[ponbac]

When a monorepo root is added as a project, /api/project-favicon only checks the repo root and a few fixed source paths. If the actual app lives under apps/*, the sidebar falls back to the generic folder icon even when that app has a valid favicon.

Repro:

1. Create a monorepo with an app under apps/web.
2. Add a valid favicon such as apps/web/public/favicon.svg.
3. Add the monorepo root as the project in t3code.

Expected:
If no root favicon exists, t3code should search common nested workspace roots such as apps/* and use the first valid favicon it finds.