feat: add packages/spa as React Router v7 + Vite SPA sample - #61

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11d5960a326750d5838078e36cf38b85af677262, actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

src/lib/middleware.ts:6:1: '../lib/auth/local-verifier.js' import is restricted from being used by a pattern.