Rework chat into Velocity-managed channels

Chat is now handled entirely by VelocityCore through channels with
separate readers and writers (Global, Local/Fight, Blue/Red fight team,
Team, ServerTeam, Alert and 1:1 direct messages). Each player has a
saved default channel; messages from other channels are tagged with
the channel name, and every default change is announced.

- /global, /local, /tc, /stc, /msg and /r switch the default channel
  when called without a message
- /chat <channel> switches, /chat <channel> join|leave toggles reading
  (saved); moderators can join arenas by name and write with
  /chat <channel> msg <text>
- '+' sends from global to local and from local/fight to the fight team
- Referees write yellow in the fight chat
- Subservers no longer receive chat; arenas get a record-only
  ChatRecordPacket so replays keep their chat
- Remove the chat listeners of SpigotCore, FightSystem, MissileWars,
  TowerRun and TNTLeague

Closes #460, #129

CommonCore/Network/src/de/steamwar/network/packets/server/ChatRecordPacket.java

@@ -0,0 +1,40 @@
+/*
+ *   This file is a part of the SteamWar software.
+ *
+ *   Copyright (C) 2026 SteamWar.de-Serverteam
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU Affero General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU Affero General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Affero General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package de.steamwar.network.packets.server;
+
+import de.steamwar.network.packets.NetworkPacket;
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+/**
+ * A chat message written on an arena. The arena only records it for the replay and never displays it.
+ */
+@NoArgsConstructor
+@AllArgsConstructor
+@EqualsAndHashCode(callSuper = true)
+@Getter
+public class ChatRecordPacket extends NetworkPacket {
+    private static final long serialVersionUID = -4718360932583127458L;
+    private int playerId;
+    private String message;
+}