Add HeXi bot codebase: custom plugins, web frontends, tests

- hexi core: message handling, rate limiting, cooldown, plugin manager
- Custom plugins: BF stats, daily check-in, quotes, persona cards, etc.
- Community plugins vendored under hexi/plugins with local fixes
- Web admin frontends (learning-chat, persona-admin), unified hexi/web
- Tests for rate_limit/cooldown/memes/persona; poetry.lock

Co-Authored-By: Claude <noreply@anthropic.com>

hexi/plugins/nonebot_plugin_group_tools/utils/message.py

@@ -0,0 +1,13 @@
+from nonebot.adapters.onebot.v11 import GroupMessageEvent
+
+
+def get_at_id(ev: GroupMessageEvent) -> int | None:
+    """提取消息中第一个被 at 的用户(排除 at all)"""
+    for m in ev.message:
+        if m.type == "at" and m.data.get("qq") != "all":
+            return int(m.data["qq"])
+    return None
+
+
+def has_at_all(ev: GroupMessageEvent) -> bool:
+    return any(m.type == "at" and m.data.get("qq") == "all" for m in ev.message)