Fixes messages that 6.4.0 turned into text like "[B@7fad8c79".

• If you upgraded to 6.4.0 and your messages contained decorative characters (for example the fullwidth brackets 【 】), they were saved garbled during the config.properties import. 6.4.1 repairs them automatically on its first start and writes the corrected config.yml back; the log tells you how many messages were fixed. Nothing else in the file is touched.
• Upgrading straight from 6.3.x now imports config.properties with the correct character encoding, so this cannot happen again.
• Only the player-facing and notification messages are repaired. Webhook URLs, tokens, chat ids, console commands and database settings are never modified.