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-certificate.php

@@ -125,6 +125,24 @@ final class M365_Login_Certificate {
 		);
 	}
 
+	/**
+	 * Exactly one certificate re-exported from a PEM text, or '' if none can be read.
+	 *
+	 * @param string $pem PEM text (may contain other blocks).
+	 * @return string
+	 */
+	public static function clean_pem( $pem ) {
+		if ( ! preg_match( '/-----BEGIN CERTIFICATE-----.+?-----END CERTIFICATE-----/s', (string) $pem, $m ) ) {
+			return '';
+		}
+		$cert  = openssl_x509_read( $m[0] );
+		$clean = '';
+		if ( false === $cert || ! openssl_x509_export( $cert, $clean ) ) {
+			return '';
+		}
+		return self::normalise_pem( $clean );
+	}
+
 	/**
 	 * Normalises line endings and trims a PEM block.
 	 *