Fix Integrasi tab layout and add save button

- Make email test inputs 50/50 with flex-1 classes
- Add save button back to Integrasi tab
- Improve button styling with border-top-2 for better separation
- Update save button text to 'Simpan Semua Pengaturan'

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/components/admin/settings/IntegrasiTab.tsx

@@ -366,15 +366,15 @@ export function IntegrasiTab() {
                   </div>
                 </div>
 
-                <div className="flex gap-2 pt-4 border-t">
+                <div className="flex gap-4 pt-4 border-t">
                   <Input
                     type="email"
                     value={testEmail}
                     onChange={(e) => setTestEmail(e.target.value)}
                     placeholder="Email uji coba"
-                    className="border-2 max-w-xs"
+                    className="border-2 flex-1"
                   />
-                  <Button variant="outline" onClick={sendTestEmail} className="border-2" disabled={sendingTest}>
+                  <Button variant="outline" onClick={sendTestEmail} className="border-2 flex-1" disabled={sendingTest}>
                     <Send className="w-4 h-4 mr-2" />
                     {sendingTest ? 'Mengirim...' : 'Kirim Email Uji Coba'}
                   </Button>
@@ -439,9 +439,11 @@ export function IntegrasiTab() {
         </CardContent>
       </Card>
 
-      <Button onClick={saveSettings} disabled={saving} className="shadow-sm">
-        {saving ? 'Menyimpan...' : 'Simpan Pengaturan'}
-      </Button>
+      <div className="flex gap-4 pt-4 border-t-2 border-border">
+        <Button onClick={saveSettings} disabled={saving} className="shadow-sm flex-1">
+          {saving ? 'Menyimpan...' : 'Simpan Semua Pengaturan'}
+        </Button>
+      </div>
     </div>
   );
 }