Migrate FightSystem modes and countdowns to GameCore

- Move shared arena-mode abstractions into GameCore
- Adapt fight countdowns and APIs to the shared model
- Add SteamWar issue audit workflow and SQL language settings

TNTLeague/build.gradle.kts

@@ -27,6 +27,7 @@ kotlin {
 
 dependencies {
     compileOnly(libs.paperapi)
+    compileOnly(project(":GameCore", "default"))
     compileOnly(project(":SpigotCore", "default"))
     compileOnly(project(":KotlinCore", "default"))
-}
+}