feat: Comprehensive mobile UI improvements

Dashboard mobile changes:
- Sidebar becomes slide-out drawer with overlay
- Added mobile filter toggle button
- Table wrapped for horizontal scroll
- Stats grid: 2 columns on tablet, 1 on phone
- Larger touch targets (44px minimum)
- Full-width modals with better spacing
- Admin dropdown slides up from bottom
- Fixed bulk action bar at bottom

Ticket page mobile changes:
- Stack metadata vertically
- Full-width buttons and inputs
- Scrollable tabs
- Better comment form layout
- Improved timeline readability

General:
- Prevent iOS zoom with 16px input font
- Touch-friendly spacing throughout

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

views/DashboardView.php

@@ -357,6 +357,7 @@
                 <?php endif; ?>
 
                 <!-- Table -->
+                <div class="table-wrapper">
                 <table>
         <thead>
             <tr>
@@ -445,6 +446,7 @@
             ?>
         </tbody>
                 </table>
+                </div><!-- End table-wrapper -->
             </div>
         </div>
     </div>