Release v0.6.2

Added

• Auto-update check on startup with 1-hour cache to detect new releases
• Interactive upgrade prompt when update is available (upgrade now / skip)
• --upgrade command for one-click bot updates via git pull and dependency reinstall
• Version comparison logic to determine if update is needed
• Graceful handling of network failures during update check

Changed

• Updated README.md and README-zh.md with upgrade command documentation
• Added auto-update feature to Operations section in documentation