feat(miniprogram): 用户协议 + 隐私政策页面，登录需勾选同意

- 新增 legal/user-agreement 和 legal/privacy-policy 页面
- 登录页增加协议勾选复选框（未勾选时拦截登录/绑定）
- 协议链接可点击跳转查看全文
- RichText 渲染 HTML 格式协议内容

apps/miniprogram/src/pages/login/index.scss

@@ -63,3 +63,44 @@
 .login-body {
   width: 100%;
 }
+
+.agreement-row {
+  display: flex;
+  align-items: flex-start;
+  margin-top: 32px;
+  gap: 12px;
+}
+
+.checkbox {
+  width: 32px;
+  height: 32px;
+  border: 2px solid rgba(255, 255, 255, 0.6);
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  flex-shrink: 0;
+  margin-top: 2px;
+}
+
+.checkbox.checked {
+  background: white;
+  border-color: white;
+}
+
+.check-mark {
+  font-size: 22px;
+  color: $pri;
+  font-weight: bold;
+}
+
+.agreement-text {
+  font-size: 24px;
+  color: rgba(255, 255, 255, 0.8);
+  line-height: 1.6;
+}
+
+.agreement-link {
+  color: white;
+  font-weight: bold;
+}