[chestshop] Remove MineDown + multi-language; move messaging to HiberniaFramework i18n

ChestShop's transaction/info messages crashed at runtime (IncompatibleClassChangeError): the bundled de.themoep MineDown library has an internal type (Util$TextControl) that implements net.kyori.adventure.text.format.TextFormat, which is now a sealed interface in modern Adventure — incompatible whether Adventure is bundled (relocated) or native. The earlier "use Paper's native Adventure" change only deferred it (the plugin had previously died at enable on a missing Adventure class, before any message was sent).

Fix (the fork doesn't need multi-language support): rip out MineDown and the de.themoep LanguageManager entirely and move ChestShop messaging onto the same HiberniaFramework i18n stack Treasury/Business use.

• Deleted the 48 languages/lang.*.yml files; English text now lives in messages.properties (MiniMessage + {placeholder}), backed by the framework Message bean.
• Messages is now a thin adapter over ChestShop.message() (the framework Message) — its public API is unchanged, so the ~28 call sites are untouched. Item icons render via a ComponentLike {item} placeholder (message.component(key, "item", itemComponent, …)), replacing MineDown's Replacer.
• Raw item-info lines (lore/enchant/potion, §-coded) deserialize via LegacyComponentSerializer.legacySection().
• Dropped the bundled+relocated Adventure, adventure-platform-bukkit/BukkitAudiences, MineDown and lang-bukkit deps; Adventure is now Paper-native (compileOnly serializers). Jar shrinks further.

Verified: ChestShop enables; the framework loads all chestshop.* keys; market tracker starts; no IncompatibleClassChangeError. In-game buy/sell still wants a manual smoke test, but the offending library is gone.