Replace BTCPay payments with free pre-orders + live ready-status

- server.js: order store with K484-XXXX codes, stand assignment, SSE
  status to customers, passcode-gated staff API, persists to .data/
- staff.html at /staff: order board with Mark ready / Collected / Cancel
- index.html: drop BTCPay API key, invoices, QR, BTC price; orders now
  server-backed with live PREPARING -> READY updates and stand location
- e2e-test.js rewritten for the order loop (14 checks, all passing)
- README added; .gitignore covers server/.data

README.md

@@ -0,0 +1,34 @@
+# KITCHEN 484 · Solarpunk Summit
+
+Festival kitchen site: browse the food schedule, place a free pre-order,
+and watch it flip to **READY** the moment the kitchen fires it — with the
+stand to pick it up from.
+
+## What it is
+
+- `index.html` — customer PWA (schedule, cart, pickup codes, live status)
+- `server/server.js` — zero-dependency Node backend: order store, pickup
+  codes (`K484-XXXX`), SSE live status, static hosting
+- `server/staff.html` — staff order board at `/staff` (passcode-gated:
+  mark orders READY / COLLECTED / CANCELLED, filter by stand)
+- `home.html` — K484 association page (separate, untouched)
+
+Payments were removed (Sep 2026): pre-orders are free reservations;
+people pay at the stand. The old BTCPay proxy lives in git history
+(commit `601c85f`) if it's ever needed again.
+
+## Run
+
+```sh
+cd server
+cp .env.example .env   # set STAFF_PASSCODE (openssl rand -hex 4)
+node server.js         # http://localhost:8787
+```
+
+Orders persist to `server/.data/orders.json` (gitignored).
+
+## Test
+
+```sh
+cd server && npm run test:e2e   # 14 checks: order loop, auth, SSE, restart persistence
+```