Add persistent player stats and DB support

Introduce MySQL persistence and an in-memory stats system with async saving.

- Add HikariCP & MySQL connector dependencies and relocate libs in build.gradle.kts.
- Add DatabaseManager (HikariCP) to manage connection pool and lifecycle.
- Add PlayerStats data model and PlayerStatsRepository for table creation, reads, upserts and batch upserts (with prepared statements).
- Add StatsManager: coroutine-based cache, dirty-flags, async batch saves, auto-save (every 5 minutes), load/save APIs and shutdown save.
- Add StatsListener: load on AsyncPlayerPreLoginEvent and save on PlayerQuitEvent.
- Wire DB and stats into main plugin: connect on enable (disable plugin on fail), initialize StatsManager, save/disconnect on disable, register leaderboard command and stats listener.
- Update GameManager to record kills/wins/deaths and adjust scrimScore on events.
- Add LeaderboardCommand and language entries for leaderboard output; expose command in plugin.yml.
- Add database configuration section to config.yml.
- Minor refactor: KitCommand plugin accessor changed to a getter.

These changes provide a robust, pooled DB connection and efficient stats persistence (batched/upserted) to reduce DB load and ensure data safety during shutdown.

src/main/kotlin/club/mcscrims/speedhg/game/GameManager.kt

@@ -226,6 +226,15 @@ class GameManager(
 		alivePlayers.remove( player.uniqueId )
 		player.gameMode = GameMode.SPECTATOR
 
+		plugin.statsManager.addDeath( player.uniqueId )
+		plugin.statsManager.adjustScrimScore( player.uniqueId, -25 ) // Elo-Verlust
+
+		if ( killer != null )
+		{
+			plugin.statsManager.addKill( killer.uniqueId )
+			plugin.statsManager.adjustScrimScore( killer.uniqueId, +15 ) // Elo-Gewinn
+		}
+
 		player.inventory.contents.filterNotNull().forEach {
 			player.world.dropItemNaturally( player.location, it )
 		}
@@ -257,6 +266,17 @@ class GameManager(
 	) {
 		setGameState( GameState.ENDING )
 		timer = 15
+
+		val winnerUUID = alivePlayers.firstOrNull()
+
+		Bukkit.getOnlinePlayers().forEach { p ->
+			if ( p.uniqueId == winnerUUID )
+			{
+				plugin.statsManager.addWin( p.uniqueId )
+				plugin.statsManager.adjustScrimScore( p.uniqueId, +50 ) // Elo-Bonus für Win
+			}
+		}
+
 		plugin.kitManager.clearAll()
 
 		Bukkit.getOnlinePlayers().forEach { p ->