feat: 完善工作台展示场景 - 新增 Modal/Toast 组件、EmptyState 使用、确认弹窗、筛选分页

- 新增 Modal 确认弹窗组件和 Toast 消息提示组件
- 在 SkillsPage、LogsPage、TasksPage、ProjectsPage 使用 EmptyState
- 为删除任务、取消订阅、移除成员、技能订阅添加确认弹窗
- 丰富聊天场景：代码展示、表格数据、多轮对话、错误提示
- 优化 ChatPage 布局，修复对话区域滚动问题
- 为 ProjectsPage 添加筛选卡片和分页组件
- 添加表单校验错误状态展示
- 同步 specs 到主目录

src/styles/global.scss

@@ -1058,6 +1058,7 @@ input:checked + .slider:before {
     display: flex;
     flex-direction: column;
     height: 100%;
+    min-height: 0;
     background: var(--color-bg-1);
 }
 
@@ -1272,6 +1273,8 @@ input:checked + .slider:before {
     display: flex;
     flex-direction: column;
     background: var(--color-bg-1);
+    min-height: 0;
+    overflow: hidden;
 }
 
 .chat-messages {
@@ -2542,3 +2545,174 @@ input:checked + .slider:before {
 .message-thinking {
     cursor: pointer;
 }
+
+/* ===== Modal 弹窗样式 ===== */
+.modal-overlay {
+    position: fixed;
+    top: 0;
+    left: 0;
+    right: 0;
+    bottom: 0;
+    background: rgba(15, 23, 42, 0.45);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    z-index: 2000;
+    backdrop-filter: blur(2px);
+}
+
+.modal {
+    background: var(--color-bg-1);
+    border-radius: var(--radius-lg);
+    box-shadow: 0 8px 32px rgba(15, 23, 42, 0.16);
+    width: 420px;
+    max-width: 90vw;
+    animation: modal-in 0.2s ease-out;
+}
+
+@keyframes modal-in {
+    from {
+        opacity: 0;
+        transform: scale(0.96);
+    }
+    to {
+        opacity: 1;
+        transform: scale(1);
+    }
+}
+
+.modal-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    padding: 16px 20px;
+    border-bottom: 1px solid var(--color-border-2);
+}
+
+.modal-title {
+    font-size: 16px;
+    font-weight: 600;
+    color: var(--color-text-1);
+}
+
+.modal-close {
+    width: 28px;
+    height: 28px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    border-radius: var(--radius-sm);
+    cursor: pointer;
+    color: var(--color-text-3);
+    transition: all 0.2s;
+
+    &:hover {
+        background: var(--color-bg-2);
+        color: var(--color-text-1);
+    }
+}
+
+.modal-body {
+    padding: 20px;
+    font-size: 14px;
+    color: var(--color-text-2);
+    line-height: 1.6;
+}
+
+.modal-footer {
+    display: flex;
+    justify-content: flex-end;
+    gap: 8px;
+    padding: 12px 20px;
+    border-top: 1px solid var(--color-border-2);
+}
+
+/* ===== Toast 消息提示样式 ===== */
+.toast {
+    position: fixed;
+    top: 20px;
+    left: 50%;
+    transform: translateX(-50%);
+    display: flex;
+    align-items: center;
+    gap: 10px;
+    padding: 12px 16px;
+    border-radius: var(--radius-md);
+    box-shadow: 0 4px 16px rgba(15, 23, 42, 0.12);
+    z-index: 3000;
+    animation: toast-in 0.3s ease-out;
+    font-size: 14px;
+    font-weight: 500;
+}
+
+@keyframes toast-in {
+    from {
+        opacity: 0;
+        transform: translateX(-50%) translateY(-10px);
+    }
+    to {
+        opacity: 1;
+        transform: translateX(-50%) translateY(0);
+    }
+}
+
+.toast-success {
+    background: var(--color-success-light);
+    color: var(--color-success);
+    border: 1px solid rgba(16, 185, 129, 0.2);
+}
+
+.toast-error {
+    background: var(--color-danger-light);
+    color: var(--color-danger);
+    border: 1px solid rgba(239, 68, 68, 0.2);
+}
+
+.toast-warning {
+    background: var(--color-warning-light);
+    color: var(--color-warning);
+    border: 1px solid rgba(245, 158, 11, 0.2);
+}
+
+.toast-info {
+    background: var(--color-primary-light);
+    color: var(--color-primary);
+    border: 1px solid rgba(59, 130, 246, 0.2);
+}
+
+.toast-icon {
+    display: flex;
+    align-items: center;
+    font-size: 16px;
+}
+
+.toast-message {
+    flex: 1;
+}
+
+.toast-close {
+    display: flex;
+    align-items: center;
+    cursor: pointer;
+    opacity: 0.7;
+    transition: opacity 0.2s;
+
+    &:hover {
+        opacity: 1;
+    }
+}
+
+/* ===== 表单校验错误样式 ===== */
+.form-control.is-invalid {
+    border-color: var(--color-danger);
+
+    &:focus {
+        box-shadow: 0 0 0 2px rgba(239, 68, 68, 0.1);
+    }
+}
+
+.form-error {
+    font-size: 12px;
+    color: var(--color-danger);
+    margin-top: 4px;
+}