Update default Create Next App favicon (#97634)
## Summary
Replace the Vercel triangle favicon in all non-empty default Create Next
App templates with the same Next.js favicon used on nextjs.org. This
gives new Next.js apps Next.js branding in the browser tab while leaving
the Vercel deployment call to action unchanged.
## Verification
- `pnpm --filter=create-next-app build`
- Generated App Router and Pages Router starters with `--skip-install`
and verified that their emitted favicon matches
`https://nextjs.org/favicon.ico` across all eight template variants.
<!-- NEXT_JS_LLM -->
