Configure Vercel deployment for admin app and update Next.js config #4097

Originally written by @ccantynz-alt on GitHub.
Imported from https://github.com/ccantynz-alt/AlecRae.com/pull/34

Description

This PR adds Vercel deployment configuration for the admin app and updates the Next.js configuration to use the stable typedRoutes API.

Changes:

• Added vercel.json configuration file specifying the build setup for Vercel deployment (using bun for install/build, Next.js framework)
• Moved typedRoutes from the experimental config object to the stable top-level configuration in next.config.ts, as this feature is no longer experimental in the Next.js version being used

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactor (no functional changes)
• Documentation update
• Infrastructure / CI change

Testing

No testing needed. These are configuration changes:

• Vercel deployment config is declarative and will be validated by Vercel during deployment
• Next.js config change is a straightforward API migration to a stable feature; existing type-safe routes functionality remains unchanged

Checklist

• My code follows the project style guidelines
• I have performed a self-review of my code
• Lint and type-check pass (bun run lint && bun run typecheck)

Breaking changes

N/A

https://claude.ai/code/session_011kd5gcHiRgj3xCih6wvHCo