Fix the findings of the third security audit

- Privileged accounts: the UPN rule also applies when bind_oid is off or
  the account is not bound; privileges are checked on every site of a
  multisite user, include code/HTML capabilities (unfiltered_html,
  plugins, themes, users) and the remembered roles of deactivated
  accounts.
- send_auth_cookies protection also works on WordPress 6.0/6.1.
- Run lock via INSERT IGNORE (atomic), refreshed during long runs; a
  shutdown handler reports fatal errors and frees the lock.
- Deprovisioning only for accounts linked in the current tenant (tenant
  recorded per account; legacy links not found are left alone).
- Safety stop based on the accounts linked before the run; new safety
  stop for removals of administrative roles.
- Disable is idempotent; row-action nonces are bound to the state.
- Profile photos are re-encoded to 240 px (drops EXIF and appended
  data), size-limited while downloading, removed on deactivation;
  index.php guard in the photo folder.
- Privacy exporter and eraser for the copied data.
- One-time migration hardens accounts deactivated by 1.0 and cleans a
  stored certificate bundle; the .cer download is always re-exported.
- Password fields hidden in button-only mode even when the connection
  is broken; settings written non-autoloaded; robust user ID queries.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

includes/class-m365-login-admin.php

@@ -567,7 +567,8 @@ class M365_Login_Admin {
 		}
 		check_admin_referer( self::POST_CERT );
 
-		$pem = $this->settings->certificate_pem();
+		// Only ever the re-exported public certificate, whatever an older version stored.
+		$pem = M365_Login_Certificate::clean_pem( $this->settings->certificate_pem() );
 		if ( '' === $pem ) {
 			wp_die( esc_html__( 'No certificate is stored.', 'm365-login' ), 404 );
 		}