Add menu enable toggle, user status, and mobile/UI polish

- Admin menu page: mobile item cards now put Actions in the top-right
  corner next to Status, matching the desktop row layout instead of
  stacking at the bottom; same treatment applied to announcements and
  users for consistency across all three admin lists
- Center button label text everywhere via .btn { justify-content: center }
  instead of one-off overrides
- Add a Disable/Enable Menu toggle to the admin menu toolbar; the public
  menu page shows its existing "menu being updated" message while disabled
- Add an Enabled/Disabled status to user accounts, with its own toggle
  badge, guardrails against disabling your own account or the last
  enabled account, and an immediate session kick for anyone disabled
  mid-session
- Fix the announcement banner / hero tagline "·" separators to hide only
  when their neighboring text actually wraps onto a different line,
  instead of a fixed breakpoint or always-on dot

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

inc/menu.php

@@ -7,6 +7,22 @@ declare(strict_types=1);
 
 require_once __DIR__ . '/db.php';
 
+// Whether the public menu page should show its items at all — separate
+// from any individual item's is_available, this is the admin-facing "take
+// the whole menu down for maintenance" switch. Defaults to enabled if the
+// singleton settings row is somehow missing.
+function is_menu_enabled(): bool {
+    $pdo = get_db();
+    $value = $pdo->query("SELECT menu_enabled FROM site_settings WHERE id = 1")->fetchColumn();
+    return $value === false ? true : (bool) $value;
+}
+
+function set_menu_enabled(bool $enabled): void {
+    $pdo = get_db();
+    $stmt = $pdo->prepare("UPDATE site_settings SET menu_enabled = ?, updated_at = CURRENT_TIMESTAMP WHERE id = 1");
+    $stmt->execute([$enabled ? 1 : 0]);
+}
+
 function get_full_menu(bool $availableOnly = false): array {
     $pdo = get_db();