fix: move theme save/cancel buttons outside collapsible section

Save and Cancel buttons were hidden inside the collapsible "Custom Colors"
section, so manual color changes were lost on navigation. Moved them to
the top level so they are always visible when there are unsaved changes.

src/components/admin/ThemeTab.tsx

@@ -395,11 +395,13 @@ export function ThemeTab() {
                 />
               </div>
             </div>
+          </div>
+        )}
+      </div>
 
-            {/* Save / Cancel / Reset buttons */}
-            <div className="flex flex-wrap items-center gap-3">
+      {/* Save / Cancel — always visible when there are unsaved changes */}
       {hasUnsavedChanges && (
-                <>
+        <div className="flex flex-wrap items-center gap-3">
           <button
             onClick={() => updateColorsMutation.mutate(draftColors)}
             disabled={updateColorsMutation.isPending}
@@ -416,12 +418,8 @@ export function ThemeTab() {
           >
             {t('common.cancel')}
           </button>
-                </>
-              )}
-            </div>
         </div>
       )}
-      </div>
 
       {/* Reset all colors */}
       <div className="flex justify-end">