STAND_LOCATIONS map in server.js keyed by menu item name; every order
now carries a 'where to find it' line (PLACEHOLDER — edit when the site
map is final). Staff can override per order when marking ready.
- 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
