chore: revert Lavalink timeout to 30s, add PMD + stricter checkstyle

- LavalinkManager: httpTimeout back to 30s (stagger delays are the real fix)
- checkstyle: comprehensive ruleset from LoParkour (200-line files, complexity, naming)
- PMD: ruleset with CognitiveComplexity, CloseResource, TooManyMethods etc
- Both tools run with ignoreFailures=true (warnings only, don't block build)

src/main/java/creator/loki/feature/music/core/LavalinkManager.java

@@ -55,7 +55,7 @@ public class LavalinkManager {
             .setName("main")
             .setServerUri(lavalinkConfig.getWsUri())
             .setPassword(lavalinkConfig.getPassword())
-            .setHttpTimeout(60000L)
+            .setHttpTimeout(30000L)
             .build());
 
     registerListeners();