/treasury reload should re-read config.yml + messages.properties at runtime

Add a /treasury reload subcommand that actually refreshes in-memory config and i18n without a server restart: plugin.reloadConfig(), re-process the @ConfigurationComponent POJOs via the framework ConfigurationProcessor, reload the manual config POJOs (Salary/BalanceTax/SourceIncomeTax) by re-reading their values, re-apply the log level, and Message.reload(). Note structural settings (DB pool, currency formatter, salary/tax schedule intervals) still need a restart.