Kill the static god-object surface on ChestShop.java: DI the messenger, de-static the service refs, relocate the pure helper

The plugin main class had accumulated a static service-locator/god surface. Cleaned the parts that are genuinely misplaced logic/state (leaving only true plugin infrastructure):

• sendBungeeMessage (4 static overloads + private) → new @Singleton services/BungeeMessenger injecting Message + ChestShopConfiguration + JavaPlugin. Injected into its 2 real callers (TransactionService, ShowItemHook). The unused String/BaseComponent[] overloads were dropped.
• values() (pure message-map builder, 6 callers) → pure utils/Messages.values(...). It's a pure function, so a util — not a DI bean (DI is for collaborators, not pure functions).
• static service refs message/itemCodes/accounts → message deleted (only the bungee methods used it); itemCodes/accounts de-static'd to instance fields (they're the main class's own enable-time orchestration).

Deliberately kept: the Bukkit-plugin infrastructure accessors (getBukkitLogger [69 callers], getPlugin, getBukkitServer, getVersion, getMetrics, callEvent, runInAsyncThread). A static logger accessor is legitimate plugin infra and matches Business's pattern; injecting loggers into ~30 classes would be churn without architectural gain.

:chestshop:build green; server enables cleanly (BungeeMessenger constructs via injected JavaPlugin); ChestShop suite 42/42.