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>

client/node_modules/gensync/index.js.flow

@@ -0,0 +1,32 @@
+// @flow
+
+opaque type Next = Function | void;
+opaque type Yield = mixed;
+
+export type Gensync<Args, Return> = {
+  (...args: Args): Handler<Return>,
+  sync(...args: Args): Return,
+  async(...args: Args): Promise<Return>,
+  // ...args: [...Args, Callback]
+  errback(...args: any[]): void,
+};
+
+export type Handler<Return> = Generator<Yield, Return, Next>;
+export type Options<Args, Return> = {
+  sync(...args: Args): Return,
+  arity?: number,
+  name?: string,
+} & (
+  | { async?: (...args: Args) => Promise<Return> }
+  // ...args: [...Args, Callback]
+  | { errback(...args: any[]): void }
+);
+
+declare module.exports: {
+  <Args, Return>(
+    Options<Args, Return> | ((...args: Args) => Handler<Return>)
+  ): Gensync<Args, Return>,
+
+  all<Return>(Array<Handler<Return>>): Handler<Return[]>,
+  race<Return>(Array<Handler<Return>>): Handler<Return>,
+};