Standardise ChestShop package names to lowercase

The ChestShop fork uses TitleCase package directories (Adapter, Commands, Listeners, Plugins, Database, Events, Configuration, Signs, UUIDs, Containers, Metadata, Market, Logging, Utils, and breeze's sub-packages) — non-idiomatic Java. Lowercase every package segment across the plugin (declarations, imports, FQNs, and the two Class.forName string literals in ImplementationAdapter and SignBreak), rename the directories, and update the build.gradle.kts jacoco excludes.

Exception: Listeners/Block/Break → listeners/block/breaking (the literal break is a Java reserved word). Shaded-library relocation targets (io.paradaux.chestshop.Libs.*, Metrics.BStats) are left as-is — they're shade destinations, not source packages. Verified by a clean :chestshop:plugin:build.