khalil-zero-cost-stacklisted

# Khalil Zero-Cost Stack ## Overview One architecture: **React SPA + ONE serverless function + a spreadsheet as the database**, all on one origin, on a free host. Proven in production: records, payments, expenses, generated documents, role separation and public one-time client links. **Core principle:** the spreadsheet is a real database with real rules. Break the four invariants below and it corrupts quietly. ## When to Use - Internal tool, a handful of named users, a few thousand records/year. - Owner wants to open the data in a tool they already know. - $0/month hosting is a requirement. **Do NOT use for:** public sign-up, regulated data (health, cards), real concurrency, sub-100ms responses, tens of users. Run the fit test in `references/playbook.md` §3 before agreeing. ## Stack | Layer | Choice | |---|---| | Frontend | React 19 + Vite + TS strict, oxlint, plain CSS with design tokens | | Routing | None. `main.tsx` picks a root from `window.location.pathname` | | State | Context for auth + toast; `useState`/`useMemo` in `App.tsx`. No state library | | Backend | ONE function, `export const config = { path: '/api/*' }`, hand-written regex router | | Data | Google Sheets REST + hand-rolled RS256 service-account JWT (no SDK) | | Auth | bcryptjs hashes in a `Users` tab, `jsonwebtoken` bearer tokens, 8h expiry | | Host | Netlify — static `client/dist` + function on one origin, SPA fallback redirect last | ## Repository Skeleton ``` client/ React SPA (own