Fix NewBook write mechanism, bundle push extension, remove vestigial hotel_id

- setBookingCustomFields: use bookings_update's own custom_fields array
  (confirmed from the real legacy plugin code) instead of
  instance_custom_fields_set, which was only ever proven for a different,
  unrelated plugin
- online_checkin_complete is now a configurable per-hotel custom field
  (online_checkin_complete_custom_field_id setting), not a bogus top-level
  bookings_update field NewBook would silently ignore
- Fix field-name mismatches vs a real live NewBook booking response:
  booking_arrival/departure/length, guest address (street/city/state/
  postcode/country, not a single field), phone/mobile (in contact_details,
  not top-level), and pickPrimaryGuest now checks primary_client (was
  checking fields that don't exist in the real API)
- Bundle the standalone push extension into backend/extension-src/, add
  GET /api/extension/download (zips on request via archiver) and a
  download button on the Settings page
- Remove newbook_hotel_id — vestigial from the legacy system's multi-hotel
  routing model, never actually reached NewBook's API, this stack is
  single-hotel-per-deployment so there's nothing to route between

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/extension-src/content-script.js

@@ -0,0 +1,161 @@
+// Injects a "Send to Tablet" button into each row of NewBook's "due for
+// arrival" list (bookings_lists_checkin), right under the page's own
+// Check In button. Only runs on that one page (see manifest.json's
+// content_scripts.matches) — the popup covers single-booking pages
+// (bookings_view/edit/checkin) already.
+//
+// Row markup, booking-ID extraction, and the "generic_button_1"-is-not-
+// actually-unique gotcha are all confirmed from a real sample row the user
+// provided 2026-09-01 (see project_checkin memory) — not guessed. NewBook's
+// own Check In button uses a non-unique id (`generic_button_1` repeated
+// across every row), so this script never relies on ids from NewBook's own
+// markup — only class/attribute selectors scoped per row, and its own
+// injected elements get ids built from the booking ID
+// (`tcp-btn-<bookingId>`) to stay collision-free and support idempotent
+// re-injection checks.
+//
+// MutationObserver pattern (watching for AJAX-refreshed rows, not just
+// initial page load) is the same approach chrome-newbook-assistant already
+// had to use for this same NewBook UI (~/laptop-archive) — this system
+// clearly refreshes table content via AJAX (see the `via_ajax` tooltip
+// classes in the sample row) without a full page reload, so a one-time scan
+// on document_idle alone would miss rows added/replaced afterward.
+
+const PROCESSED_ATTR = 'data-tcp-processed';
+
+function extractBookingId(row) {
+  const checkbox = row.querySelector('input.booking_id_checkbox');
+  if (checkbox?.value) return checkbox.value;
+  // Fallback: class name carries it too (`booking_37117`) — confirmed from
+  // the sample row, kept as a fallback in case a future NewBook markup
+  // change drops the checkbox but keeps the class.
+  const match = row.className.match(/\bbooking_(\d+)\b/);
+  return match ? match[1] : null;
+}
+
+function extractGuestName(row) {
+  // The guest/company link's own text node — tooltip content is a sibling
+  // element (easytooltip_content), not part of the visible text, so a plain
+  // textContent read on the link itself would double up with it. Grab just
+  // the first non-empty text child instead.
+  const link = row.querySelector('a.easytooltip[class*="booking_"]');
+  if (!link) return '';
+  for (const node of link.childNodes) {
+    if (node.nodeType === Node.TEXT_NODE && node.textContent.trim()) {
+      return node.textContent.trim();
+    }
+  }
+  return link.textContent.trim();
+}
+
+function findCheckInCell(row) {
+  const btn = row.querySelector('button[aria-label="Check In"]');
+  return btn ? btn.closest('td') : null;
+}
+
+function makeSendButton(bookingId, guestName) {
+  const btn = document.createElement('button');
+  btn.id = `tcp-btn-${bookingId}`;
+  btn.type = 'button';
+  btn.textContent = 'Send to Tablet';
+  btn.style.cssText = `
+    display: block; margin-top: 6px; width: 100%;
+    padding: 4px 8px; font-size: 12px; font-weight: 600;
+    background: #be123c; color: #fff; border: none; border-radius: 6px;
+    cursor: pointer; font-family: -apple-system, BlinkMacSystemFont, sans-serif;
+  `;
+  btn.addEventListener('click', e => {
+    e.preventDefault();
+    e.stopPropagation();
+    togglePanel(btn, bookingId, guestName);
+  });
+  return btn;
+}
+
+let openPanel = null;
+
+async function togglePanel(anchorBtn, bookingId, guestName) {
+  if (openPanel) { openPanel.remove(); openPanel = null; }
+
+  const panel = document.createElement('div');
+  panel.style.cssText = `
+    margin-top: 6px; padding: 8px; background: #f4f5f7; border: 1px solid #e4e8ee;
+    border-radius: 8px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;
+    font-size: 12px; color: #1e293b;
+  `;
+  panel.textContent = 'Loading tablets…';
+  anchorBtn.insertAdjacentElement('afterend', panel);
+  openPanel = panel;
+
+  const res = await chrome.runtime.sendMessage({ action: 'tcpListDevices' });
+  if (!res?.ok) {
+    panel.textContent = `Could not load tablets: ${res?.error || 'not configured yet — see extension Settings'}`;
+    return;
+  }
+  if (!res.devices.length) {
+    panel.textContent = 'No tablets registered yet.';
+    return;
+  }
+
+  const select = document.createElement('select');
+  select.style.cssText = 'width: 100%; margin-bottom: 6px; padding: 4px;';
+  select.innerHTML = res.devices.map(d =>
+    `<option value="${d.device_id}" ${d.status === 'busy' ? 'disabled' : ''}>${escapeHtml(d.name)}${d.status === 'busy' ? ' (busy)' : ''}</option>`
+  ).join('');
+
+  const sendBtn = document.createElement('button');
+  sendBtn.textContent = `Send${guestName ? ` — ${guestName}` : ''}`;
+  sendBtn.style.cssText = `
+    width: 100%; padding: 4px 8px; background: #c9a84c; color: #1a1a2e;
+    border: none; border-radius: 6px; font-weight: 600; cursor: pointer;
+  `;
+  sendBtn.addEventListener('click', async () => {
+    sendBtn.disabled = true;
+    sendBtn.textContent = 'Sending…';
+    const result = await chrome.runtime.sendMessage({
+      action: 'tcpPush', bookingId, deviceId: select.value,
+    });
+    if (result?.ok) {
+      panel.textContent = 'Sent — the tablet should navigate now.';
+    } else {
+      panel.textContent = `Failed: ${result?.error || 'unknown error'}`;
+    }
+  });
+
+  panel.innerHTML = '';
+  panel.appendChild(select);
+  panel.appendChild(sendBtn);
+}
+
+function escapeHtml(s) {
+  const div = document.createElement('div');
+  div.textContent = s;
+  return div.innerHTML;
+}
+
+function processRow(row) {
+  if (row.hasAttribute(PROCESSED_ATTR)) return;
+  const bookingId = extractBookingId(row);
+  const cell = findCheckInCell(row);
+  if (!bookingId || !cell) return; // not a real booking row, or no Check In button in it
+
+  row.setAttribute(PROCESSED_ATTR, '1');
+  cell.appendChild(makeSendButton(bookingId, extractGuestName(row)));
+}
+
+function scanForRows(root = document) {
+  root.querySelectorAll('tr.checkbox_row').forEach(processRow);
+}
+
+scanForRows();
+
+const observer = new MutationObserver(mutations => {
+  for (const m of mutations) {
+    for (const node of m.addedNodes) {
+      if (node.nodeType !== Node.ELEMENT_NODE) continue;
+      if (node.matches?.('tr.checkbox_row')) processRow(node);
+      else scanForRows(node);
+    }
+  }
+});
+observer.observe(document.body, { childList: true, subtree: true });