feat(housekeeping): force-disconnect-user packet

Incoming 9106 HousekeepingForceDisconnectUserEvent — (userId, reason).
Sends the optional reason as a Habbo.alert, dispatches the action ack
BEFORE calling target.disconnect() so the result lands on the wire
before the target's socket closes, then drops the session. Online-only;
offline target returns `user_offline`.

`mvn compile` clean.

Emulator/src/main/java/com/eu/habbo/messages/PacketManager.java

@@ -724,5 +724,6 @@ public class PacketManager {
         this.registerHandler(Incoming.HousekeepingUnbanUserEvent, com.eu.habbo.messages.incoming.housekeeping.HousekeepingUnbanUserEvent.class);
         this.registerHandler(Incoming.HousekeepingMuteUserEvent, com.eu.habbo.messages.incoming.housekeeping.HousekeepingMuteUserEvent.class);
         this.registerHandler(Incoming.HousekeepingKickUserEvent, com.eu.habbo.messages.incoming.housekeeping.HousekeepingKickUserEvent.class);
+        this.registerHandler(Incoming.HousekeepingForceDisconnectUserEvent, com.eu.habbo.messages.incoming.housekeeping.HousekeepingForceDisconnectUserEvent.class);
     }
 }

Emulator/src/main/java/com/eu/habbo/messages/incoming/Incoming.java

@@ -468,4 +468,5 @@ public class Incoming {
     public static final int HousekeepingUnbanUserEvent = 9103;
     public static final int HousekeepingMuteUserEvent = 9104;
     public static final int HousekeepingKickUserEvent = 9105;
+    public static final int HousekeepingForceDisconnectUserEvent = 9106;
 }

Emulator/src/main/java/com/eu/habbo/messages/incoming/housekeeping/HousekeepingForceDisconnectUserEvent.java

@@ -0,0 +1,54 @@
+package com.eu.habbo.messages.incoming.housekeeping;
+
+import com.eu.habbo.Emulator;
+import com.eu.habbo.habbohotel.permissions.Permission;
+import com.eu.habbo.habbohotel.users.Habbo;
+import com.eu.habbo.messages.incoming.MessageHandler;
+import com.eu.habbo.messages.outgoing.housekeeping.HousekeepingActionResultComposer;
+
+/**
+ * Force-close the session of an online user. Unlike kick (which only
+ * removes them from the current room), this drops their socket. Equivalent
+ * to /disconnect in command form but issued through the HK panel.
+ */
+public class HousekeepingForceDisconnectUserEvent extends MessageHandler {
+    private static final String ACTION_KEY = "user.disconnect";
+
+    @Override
+    public int getRatelimit() {
+        return 1000;
+    }
+
+    @Override
+    public void handle() throws Exception {
+        if (!this.client.getHabbo().hasPermission(Permission.ACC_HOUSEKEEPING)) {
+            return;
+        }
+
+        int userId = this.packet.readInt();
+        String reason = this.packet.readString();
+
+        if (userId <= 0) {
+            this.client.sendResponse(new HousekeepingActionResultComposer(ACTION_KEY, false, 0, "invalid_input"));
+            return;
+        }
+
+        Habbo target = Emulator.getGameEnvironment().getHabboManager().getHabbo(userId);
+
+        if (target == null) {
+            this.client.sendResponse(new HousekeepingActionResultComposer(ACTION_KEY, false, 0, "user_offline"));
+            return;
+        }
+
+        if (reason != null && !reason.isEmpty()) {
+            target.alert(reason);
+        }
+
+        // ACK first so the action result lands before the target's socket
+        // closes (otherwise an alerted user on the same emulator thread may
+        // already be torn down when we try to write).
+        this.client.sendResponse(new HousekeepingActionResultComposer(ACTION_KEY, true, userId, ""));
+
+        target.disconnect();
+    }
+}