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/web_hub_auth.py

@@ -0,0 +1,12 @@
+# -*- coding: utf-8 -*-
+"""兼容 shim：统一鉴权已迁移到 hexi.web_auth（OAuth2 + SQLite）。"""
+from hexi.web_auth import (  # noqa: F401
+    authenticate,
+    create_user,
+    get_user_by_token,
+    init_auth_db,
+    issue_token,
+    oauth2_scheme,
+    require_admin,
+    revoke_token,
+)