chore: update dependencies, remove auth

[gameroman]

Summary by CodeRabbit

• Removed Features

  • Login page, GitHub sign-in, and related authentication flows
  • User dashboard, session management, API routes, and database-backed auth/schema

• Infrastructure

  • CI workflow updated to newer action versions and build label simplified
  • Development tooling and package metadata upgraded; lint/check and config presets streamlined
  • .vercel is no longer ignored

• Tests

  • Improved userscript bundling test assertions and added dev-mode fixture