Dedupe menu admin CSS/markup, restore Mark Sold Out/Available labels

CSS redundancy cleanup on the online menu management feature:

- .menu-category was a byte-for-byte duplicate of the existing .panel
  class (background/border/border-radius/padding); folds it into
  .panel's shared selector group instead, keeping only what's not
  shared (no margin-bottom, since these sit in a grid whose own gap
  already spaces them)
- Several inline style="..." attributes were hand-copied verbatim
  between admin/menu.php's PHP template and admin/menu.js's client-
  side row/panel templates (price/sort/description cell formatting,
  category heading spacing, the empty-state row). Replaced with real
  CSS classes (.item-price-cell, .item-sort-cell, .item-desc-cell,
  .cat-name-heading, .cat-desc-text, .no-items-row td) so the styling
  lives in one place instead of two
- class="font-mono" was referenced four times but never defined
  anywhere in CSS (silently doing nothing); it's now a real one-line
  utility, which also fixes two previously-dead uses of it already
  sitting in admin/index.php
- .form-actions already existed as a class with its own margin-top,
  but every usage (two new modals here, plus a pre-existing one in
  admin/index.php) redundantly re-specified layout via inline style
  with a slightly different margin-top value each time; extended the
  shared class to own the whole pattern and dropped all three inline
  overrides
- Removed a no-op `justify-content: flex-start` (the default value)
  from the new .admin-toolbar

Caught and fixed a regression from the above before it shipped:
removing the inline margin-bottom override on the category heading
exposed that .panel h2's margin-bottom (from the existing panel
styles) has higher specificity than a bare .cat-name-heading class,
so the heading would have rendered with 5x the intended spacing.
Rescoped as .category-panel .cat-name-heading to reliably win.

Also restores the "Mark Sold Out" / "Mark Available" button wording
(both directions of the toggle, in both the PHP-rendered rows and
the two JS render paths) after it had been shortened to just "Sold
Out" / "Available".

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

admin/index.php

@@ -176,7 +176,7 @@ $today = date('Y-m-d');
               </div>
             </div>
 
-            <div class="form-actions" style="display: flex; gap: 0.75rem; align-items: center;">
+            <div class="form-actions">
               <button type="submit" class="btn btn-primary">Save Announcement</button>
               <a href="index.php" class="btn btn-outline">Cancel</a>
             </div>