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/menu.php

@@ -193,6 +193,7 @@ $menuGrouped = get_full_menu(false);
         <a href="index.php">Announcements</a>
         <a href="menu.php" class="active">Menu</a>
         <a href="users.php">Users</a>
+        <a href="hours.php">Hours</a>
       </div>
       <div class="admin-user">
         <span>Logged in as <strong><?= htmlspecialchars($user['username']) ?></strong></span>
@@ -231,7 +232,7 @@ $menuGrouped = get_full_menu(false);
                   <span><?= htmlspecialchars($category['name']) ?></span>
                 </h2>
                 <p class="muted cat-desc-text"><?= htmlspecialchars($category['description'] ?? '') ?></p>
-                <div class="admin-table-actions">
+                <div class="row-actions">
                   <div class="action-stack">
                     <button type="button" class="btn btn-outline btn-sm btn-icon btn-move-cat" data-direction="up" data-id="<?= (int) $category['id'] ?>" aria-label="Move <?= htmlspecialchars($category['name']) ?> category up" <?= $catIndex === 0 ? 'disabled' : '' ?>>↑</button>
                     <button type="button" class="btn btn-outline btn-sm btn-icon btn-move-cat" data-direction="down" data-id="<?= (int) $category['id'] ?>" aria-label="Move <?= htmlspecialchars($category['name']) ?> category down" <?= $catIndex === $catCount - 1 ? 'disabled' : '' ?>>↓</button>
@@ -284,7 +285,7 @@ $menuGrouped = get_full_menu(false);
                           <?= htmlspecialchars($item['price']) ?>
                         </div>
                         <div data-label="Actions">
-                          <div class="admin-table-actions">
+                          <div class="row-actions">
                             <div class="action-stack">
                               <button type="button" class="btn btn-outline btn-sm btn-icon btn-move-item" data-direction="up" aria-label="Move <?= htmlspecialchars($item['name']) ?> up" <?= $itemIndex === 0 ? 'disabled' : '' ?>>↑</button>
                               <button type="button" class="btn btn-outline btn-sm btn-icon btn-move-item" data-direction="down" aria-label="Move <?= htmlspecialchars($item['name']) ?> down" <?= $itemIndex === $itemCount - 1 ? 'disabled' : '' ?>>↓</button>