feat: instance system settings page with risk docs, export and transfer

顶栏新增系统设置；风控说明读取 .env；数据导出与资金划转迁入三张卡片；顶栏移除导出条与手动划转。

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_instance_embed_lib.py

@@ -28,6 +28,8 @@ def test_embed_tabs_cover_main_nav():
     assert "trade" in EMBED_TABS
     assert "key_monitor" in EMBED_TABS
     assert "records" in EMBED_TABS
+    assert "settings" in EMBED_TABS
+    assert path_to_embed_tab("/settings") == "settings"
 
 
 def test_embed_context_extras_unified_ui_flags():