feat: migrate to remix v3

[mcansh]

Summary by CodeRabbit

• New Features

  • Introduced unified development workflow via vp CLI commands (dev, build, test, lint, format)

• Infrastructure & Build Changes

  • Migrated to pnpm package manager (v10.33.0) and Vite+ build system
  • Added Railway deployment configuration for streamlined hosting
  • Upgraded Node.js requirement to v24
  • Transitioned from ESLint to Oxlint and from Prettier to Oxfmt

• Refactor

  • Reorganized authentication, session, and game logic systems
  • Updated routing architecture and middleware approach
  • Consolidated configuration files and tooling