Add Milestones 1 & 2: full-stack POS foundation with admin UI

- Node/Express/TypeScript API under /api/v1 with JWT auth (login, refresh, logout, /me)
- Prisma schema: vendors, users, roles, products, categories, taxes, transactions
- SQLite for local dev; Postgres via docker-compose for production
- Full CRUD routes for vendors, users, categories, taxes, products with Zod validation and RBAC
- Paginated list endpoints scoped per vendor; refresh token rotation
- React/TypeScript admin SPA (Vite): login, protected routing, sidebar layout
- Pages: Dashboard, Catalog (tabbed Products/Categories/Taxes), Users, Vendor Settings
- Shared UI: Table, Modal, FormField, Btn, PageHeader components
- Multi-stage Dockerfile; docker-compose with Postgres healthcheck
- Seed script with demo vendor and owner account
- INSTRUCTIONS.md, ROADMAP.md, .claude/launch.json for dev server config

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/node_modules/@prisma/engines/scripts/postinstall.js

@@ -0,0 +1,28 @@
+const path = require('path')
+
+const postInstallScriptPath = path.join(__dirname, '..', 'dist', 'scripts', 'postinstall.js')
+const localInstallScriptPath = path.join(__dirname, '..', 'dist', 'scripts', 'localinstall.js')
+
+try {
+  // that's when we develop in the monorepo, `dist` does not exist yet
+  // so we compile postinstall script and trigger it immediately after
+  if (require('../package.json').version === '0.0.0') {
+    const execa = require('execa')
+    const buildScriptPath = path.join(__dirname, '..', 'helpers', 'build.ts')
+
+    execa.sync('pnpm', ['tsx', buildScriptPath], {
+      // for the sake of simplicity, we IGNORE_EXTERNALS in our own setup
+      // ie. when the monorepo installs, the postinstall is self-contained
+      env: { DEV: true, IGNORE_EXTERNALS: true },
+      stdio: 'inherit',
+    })
+
+    // if enabled, it will install engine overrides into the cache dir
+    execa.sync('node', [localInstallScriptPath], {
+      stdio: 'inherit',
+    })
+  }
+} catch {}
+
+// that's the normal path, when users get this package ready/installed
+require(postInstallScriptPath)