Refactor message-sending to use sendRichMessage API.

Replaced all instances of sendMiniMessage with sendRichMessage for improved readability and consistency across the codebase. This change ensures better handling of message formatting and placeholders.

settings.gradle.kts

@@ -14,4 +14,4 @@ pluginManagement {
     repositories {
         gradlePluginPortal()
     }
-}
+}