Each command's aliases are now configured as an `aliases` key in its own
config section (e.g. [Wx_Command] aliases = !weather, !w) rather than a
separate [Aliases] section. BaseCommand._load_aliases_from_config() reads
and injects them into keywords at startup. CommandManager.load_aliases()
and _apply_aliases() are removed. No behaviour change for commands without
aliases configured.
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