Add pub hours admin panel, rebuild announcements/users lists on CSS Grid

- Add a Hours admin panel (admin/hours.php, admin/hours.js) for editing
  the weekly open/close schedule and an optional per-day kitchen closing
  time, with a live preview of how it'll read on the public site
- Store hours in a new pub_hours table (inc/db.php), seeded with the
  site's existing Thu-Sat/9pm-kitchen schedule; inc/hours.php formats
  and groups it for display (day ranges, kitchen-close note, footer
  summary)
- Wire the public Visit card and both site footers (index.php, menu.php)
  to read hours from that data instead of hardcoded copy
- Rebuild the Announcements and Users admin tables onto the same CSS
  Grid list pattern already used for the Menu (admin-table-actions ->
  row-actions), and make the Announcements status toggle an in-place
  AJAX action like the menu item's (admin/index.js)
- Add the Hours tab to admin nav across all four admin pages

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

admin/hours.js

@@ -0,0 +1,18 @@
+// Hours admin page: purely a progressive enhancement over the plain form
+// POST that actually saves — greys out (and stops submitting) a day's time
+// fields while its "Open" box is unchecked, so a closed day can't look like
+// it still has stale hours set.
+
+document.querySelectorAll('.hours-day-row').forEach((row) => {
+  const toggle = row.querySelector('input[type="checkbox"]');
+  const timeFields = row.querySelectorAll('.day-time-field');
+
+  function applyState() {
+    timeFields.forEach((field) => {
+      field.disabled = !toggle.checked;
+    });
+  }
+
+  toggle.addEventListener('change', applyState);
+  applyState();
+});