feat: 重构学员端登录页面——专业移动端H5登录体验

LoginPanel.vue 完全重写：
- 品牌标题区：绿色圆角图标+主标题+副标题+装饰盾牌
- 表单卡片：白色圆角卡片承载手机号+短信验证码
- 图形验证码按需弹出：点击发送验证码时弹出模态弹窗
- 用户协议：自定义checkbox+协议弹窗（Tab切换）
- 倒计时持久化：localStorage按手机号存储，刷新不重置
- Toast提示：发送成功/失败/登录错误
- 辅助入口：收不到验证码/登录遇到问题弹窗
- 底部安全说明：盾牌图标+信任提示
- 输入过滤：只允许数字，16px字号防iOS缩放
- 响应式：最大420px居中，safe-area适配

styles.css：移除旧登录样式，保留全局基础

ai_knowledge_base_v2/apps/user-client/src/styles.css

@@ -51,167 +51,11 @@ button {
   color: #557066;
 }
 
+/* ── 登录页使用组件内 scoped 样式，全局仅保留基础重置 ── */
 .login-panel {
   height: 100%;
-  padding: 72px 24px 24px;
-  display: flex;
-  flex-direction: column;
-  gap: 18px;
-  background: linear-gradient(180deg, #ffffff 0%, #f3faf7 100%);
-}
-
-.brand-mark {
-  width: 56px;
-  height: 56px;
-  display: grid;
-  place-items: center;
-  border-radius: 16px;
-  background: #0f8b6f;
-  color: #ffffff;
-  font-weight: 800;
-  letter-spacing: 0;
-}
-
-.login-panel h1 {
-  margin: 10px 0 0;
-  font-size: 28px;
-  line-height: 1.2;
-}
-
-.login-panel p {
-  margin: 0 0 18px;
-  color: #5f746c;
-}
-
-.login-panel label {
-  display: grid;
-  gap: 8px;
-  color: #40524b;
-  font-size: 14px;
-}
-
-.login-panel input,
-.composer textarea {
-  width: 100%;
-  border: 1px solid #cad8d2;
-  border-radius: 14px;
-  background: #ffffff;
-  color: #17211d;
-  outline: none;
-}
-
-.login-panel input {
-  height: 48px;
-  padding: 0 14px;
-}
-
-.login-panel input:focus,
-.composer textarea:focus {
-  border-color: #0f8b6f;
-  box-shadow: 0 0 0 3px rgba(15, 139, 111, 0.12);
-}
-
-.code-row {
-  display: grid;
-  grid-template-columns: minmax(0, 1fr) 92px;
-  gap: 10px;
-}
-
-.captcha-row {
-  display: grid;
-  grid-template-columns: minmax(0, 1fr) 128px;
-  gap: 10px;
-}
-
-.captcha-image {
-  height: 48px;
-  padding: 0;
-  overflow: hidden;
-  border: 1px solid #cad8d2;
-  border-radius: 14px;
-  background: #ffffff;
-}
-
-.captcha-image img {
-  width: 100%;
-  height: 100%;
-  display: block;
-  object-fit: cover;
-}
-
-.captcha-image span {
-  color: #5f746c;
-  font-size: 13px;
-}
-
-.primary,
-.secondary,
-.send-btn,
-.stop-btn,
-.new-session-btn {
-  border: 0;
-  border-radius: 14px;
-  font-weight: 700;
-}
-
-.primary {
-  height: 50px;
-  margin-top: 8px;
-  background: #0f8b6f;
-  color: #ffffff;
-}
-
-.secondary {
-  background: #e5f3ef;
-  color: #0f735d;
-}
-
-button:disabled {
-  cursor: not-allowed;
-  opacity: 0.52;
-}
-
-.form-tip {
-  min-height: 20px;
-  color: #657970;
-  font-size: 13px;
-}
-
-.dialog-mask {
-  position: absolute;
-  inset: 0;
-  z-index: 20;
-  display: grid;
-  place-items: center;
-  padding: 24px;
-  background: rgba(12, 24, 20, 0.42);
-}
-
-.dialog-box {
-  width: min(100%, 320px);
-  padding: 22px;
-  border-radius: 18px;
-  background: #ffffff;
-  box-shadow: 0 18px 48px rgba(15, 31, 26, 0.22);
-}
-
-.dialog-box strong {
-  display: block;
-  color: #17211d;
-  font-size: 18px;
-  line-height: 1.35;
-}
-
-.dialog-box p {
-  margin: 10px 0 18px;
-  color: #51655d;
-  font-size: 14px;
-  line-height: 1.7;
-}
-
-.dialog-box .primary {
-  width: 100%;
-  margin-top: 0;
+  overflow-y: auto;
+  -webkit-overflow-scrolling: touch;
 }
 
 .topbar {