style(frontend): unify action button styles in settings lists (#185)

- Update GitHubIntegration.tsx to match BotList and TeamList button styles
- Change button size from 'sm' to 'icon' with 'h-8 w-8' class
- Replace 'space-x-2' with 'gap-1' for consistent 4px button spacing
- Remove custom padding and text color overrides
- Remove icon color classes to inherit from parent
- Add 'hover:text-error' to delete button for consistent hover effect
- All three lists (Bot, Team, Integration) now share unified button design

Author: feifei325

frontend/src/features/settings/components/GitHubIntegration.tsx

@@ -140,26 +140,24 @@ export default function GitHubIntegration() {
                         </div>
                       </div>
                     </div>
-                    <div className="flex items-center space-x-2">
+                    <div className="flex items-center gap-1">
                       <Button
                         variant="ghost"
-                        size="sm"
+                        size="icon"
                         onClick={() => handleEdit(info)}
                         title={t('integrations.edit_token')}
-                        style={{ padding: '4px' }}
-                        className="!text-text-muted hover:!text-text-primary"
+                        className="h-8 w-8"
                       >
-                        <PencilIcon className="w-4 h-4 text-text-muted" />
+                        <PencilIcon className="w-4 h-4" />
                       </Button>
                       <Button
                         variant="ghost"
-                        size="sm"
+                        size="icon"
                         onClick={() => handleDelete(info.git_domain)}
                         title={t('integrations.delete')}
-                        style={{ padding: '4px' }}
-                        className="!text-text-muted hover:!text-text-primary"
+                        className="h-8 w-8 hover:text-error"
                       >
-                        <TrashIcon className="w-4 h-4 text-text-muted" />
+                        <TrashIcon className="w-4 h-4" />
                       </Button>
                     </div>
                   </div>