feat: 榜单同步服务端（读stats+网络包下发）

BoardSyncPayload自定义包，BoardSyncManager读原版stats（挖掘总数/死亡数）构建Top10排行。顺带补回之前漏掉的BotListManager.load()。

src/main/java/com/github/zly2006/carpetslsaddition/net/BoardSyncPayload.java

@@ -0,0 +1,47 @@
+package com.github.zly2006.carpetslsaddition.net;
+
+import com.github.zly2006.carpetslsaddition.ServerMain;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+
+import java.util.List;
+
+/**
+ * 服务端 → 客户端：同步排行榜数据。
+ *
+ * <p>携带某一种榜单（死亡/挖掘）的完整排行：条目为 (玩家名, 分数)，已按分数降序。
+ * 客户端收到后缓存，供 HUD 渲染。
+ */
+public record BoardSyncPayload(String board, List<Entry> entries) implements CustomPacketPayload {
+
+    /** 单条排行数据。 */
+    public record Entry(String name, int score) {
+        public static final StreamCodec<RegistryFriendlyByteBuf, Entry> CODEC = StreamCodec.composite(
+                ByteBufCodecs.STRING_UTF8, Entry::name,
+                ByteBufCodecs.VAR_INT, Entry::score,
+                Entry::new
+        );
+    }
+
+    public static final CustomPacketPayload.Type<BoardSyncPayload> TYPE =
+            CustomPacketPayload.createType("slsa:board_sync");
+
+    public static final StreamCodec<RegistryFriendlyByteBuf, BoardSyncPayload> CODEC = StreamCodec.composite(
+            ByteBufCodecs.STRING_UTF8, BoardSyncPayload::board,
+            Entry.CODEC.apply(ByteBufCodecs.list()), BoardSyncPayload::entries,
+            BoardSyncPayload::new
+    );
+
+    @Override
+    public CustomPacketPayload.Type<? extends CustomPacketPayload> type() {
+        return TYPE;
+    }
+
+    /** 在 onInitialize 里调用，注册 payload 类型。 */
+    public static void register() {
+        net.fabricmc.fabric.api.networking.v1.PayloadTypeRegistry.playS2C().register(TYPE, CODEC);
+        ServerMain.LOGGER.info("[SLSA] registered BoardSyncPayload");
+    }
+}