feat: 添加视觉设计语言系统并重构认证页面UI

- 新增 visual_design_language.md 设计规范文档
- 新增 auth 设计 tokens (authBackground, authCard, authInput, feedback 系列等)
- 重构登录/注册/验证码/重置密码页面为新设计系统
- 新增 AuthHeroHeader, AuthSurfaceCard, AuthSection, AuthField, PasswordField 组件
- 重构 AppBanner 和 Toast 支持多类型配置 (info/success/warning/error)
- 后端 AgentScope: 重整 schemas/prompts/tools 作用域, 新增协议文档
- 更新 AGENTS.md 集成视觉设计语言约束

backend/tests/unit/v1/schedule_items/test_share.py

@@ -192,7 +192,7 @@ async def test_share_success_creates_calendar_invitation_message() -> None:
     assert message.sender_id == owner_id
     assert message.schedule_item_id == item_id
     assert message.message_type == InboxMessageType.CALENDAR
-    assert message.content == '{"type": "invite", "permission": 5, "action": "pending"}'
+    assert message.content == {"type": "invite", "permission": 5, "action": "pending"}
     session.commit.assert_awaited_once()