feat(FN-786): move Settings to last position in overflow menu

- Reorder Header overflow menu items so Settings always appears last
- Update Header.tsx to position SettingsMenuItem as the final menu entry
- Add regression tests in Header.test.tsx verifying Settings is last in all overflow states
- Add ordering tests in tablet-header-controls.test.tsx for tablet layout

packages/dashboard/app/components/Header.tsx

@@ -564,14 +564,6 @@ export function Header({
               <Clock size={16} />
               <span>Scheduled Tasks</span>
             </button>
-            <button
-              className="mobile-overflow-item"
-              onClick={() => handleOverflowAction(onOpenSettings)}
-              role="menuitem"
-            >
-              <Settings size={16} />
-              <span>Settings</span>
-            </button>
             {/* Activity Log - in overflow on mobile */}
             {onOpenActivityLog && (
               <button
@@ -620,6 +612,15 @@ export function Header({
                 <span>Missions</span>
               </button>
             )}
+            {/* Settings - always last in overflow menu */}
+            <button
+              className="mobile-overflow-item"
+              onClick={() => handleOverflowAction(onOpenSettings)}
+              role="menuitem"
+            >
+              <Settings size={16} />
+              <span>Settings</span>
+            </button>
           </div>
         )}
       </div>