v1.2.0: Implement improvement plan features

- Setback System: Teleports flagged players to lastSafeLocation (opt-in per check)
- TPS Lag Compensation: isServerLagging() helper, guards in Fly/Spider/Glide checks
- Universal Buffer System: Buffer fields for Jesus/Reach/KillAura/Timer/FastPlace/Scaffold/FastEat
- /xac debug command: Shows check-specific debug info for players
- Public API: XACApi with isFlagged(), getViolationLevel(), getTotalViolations(), isBypassed()
- Performance Metrics: /xac stats command with checks/flags/punishments tracking

src/main/java/com/xeroth/xeroanticheat/manager/MetricsManager.java

@@ -0,0 +1,51 @@
+package com.xeroth.xeroanticheat.manager;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+public class MetricsManager {
+
+    private final AtomicLong totalChecksRun = new AtomicLong();
+    private final AtomicLong totalFlagsIssued = new AtomicLong();
+    private final AtomicLong totalPunishments = new AtomicLong();
+    private long startTimeMs = System.currentTimeMillis();
+
+    public void recordCheck() {
+        totalChecksRun.incrementAndGet();
+    }
+
+    public void recordFlag() {
+        totalFlagsIssued.incrementAndGet();
+    }
+
+    public void recordPunishment() {
+        totalPunishments.incrementAndGet();
+    }
+
+    public long getTotalChecks() {
+        return totalChecksRun.get();
+    }
+
+    public long getTotalFlags() {
+        return totalFlagsIssued.get();
+    }
+
+    public long getTotalPunishments() {
+        return totalPunishments.get();
+    }
+
+    public long getUptimeSeconds() {
+        return (System.currentTimeMillis() - startTimeMs) / 1000;
+    }
+
+    public double getChecksPerSecond() {
+        long uptime = getUptimeSeconds();
+        return uptime > 0 ? (double) totalChecksRun.get() / uptime : 0;
+    }
+
+    public void reset() {
+        totalChecksRun.set(0);
+        totalFlagsIssued.set(0);
+        totalPunishments.set(0);
+        startTimeMs = System.currentTimeMillis();
+    }
+}