feat: 工作台对话列表添加删除功能

- 对话卡片 Hover 时显示删除按钮
- 点击删除按钮显示确认弹窗
- 删除按钮垂直居中对齐

src/styles/layouts/_chat-layout.scss

@@ -143,6 +143,9 @@
 }
 
 .conversation-item {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
     padding: 12px 14px;
     border-radius: var(--radius-md);
     cursor: pointer;
@@ -153,6 +156,10 @@
     &:hover {
         background: var(--color-bg-1);
         border-color: var(--color-border-2);
+
+        .conversation-item__delete {
+            opacity: 1;
+        }
     }
 
     &.active {
@@ -162,6 +169,30 @@
     }
 }
 
+.conversation-item__content {
+    flex: 1;
+    min-width: 0;
+}
+
+.conversation-item__delete {
+    flex-shrink: 0;
+    padding: 4px;
+    margin-left: 8px;
+    background: transparent;
+    border: none;
+    color: var(--color-text-3);
+    cursor: pointer;
+    opacity: 0;
+    transition: all var(--transition);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+
+    &:hover {
+        color: var(--color-danger);
+    }
+}
+
 .conversation-title {
     font-size: 14px;
     margin-bottom: 4px;