feat(ui): 创建共享 UI 组件包

将 web 和 desktop 的重复代码抽取到 @ai-assistant/ui 包:

- 添加可配置的 API 客户端 (configureApiClient)
- 迁移共享组件: ChatMessage, ChatInput, Sidebar, FileBrowser, ConfigPanel
- 迁移共享 hook: useChat
- 添加 responsive prop 支持响应式布局
- 更新 web/desktop 依赖并删除重复代码

packages/ui/src/styles/index.css

@@ -0,0 +1,115 @@
+/**
+ * Shared UI Styles
+ *
+ * 共享样式，供 web 和 desktop 包使用
+ * 注意：使用此文件时，宿主项目需要配置 Tailwind CSS
+ */
+
+/* iOS Safe Area Support */
+@supports (padding-bottom: env(safe-area-inset-bottom)) {
+  .safe-area-pb {
+    padding-bottom: calc(env(safe-area-inset-bottom) + 0.5rem);
+  }
+}
+
+/* Prevent pull-to-refresh on mobile */
+html {
+  overscroll-behavior: none;
+}
+
+/* Touch action optimization */
+.touch-pan-x {
+  touch-action: pan-x;
+}
+
+.touch-pan-y {
+  touch-action: pan-y;
+}
+
+/* Custom scrollbar */
+::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+::-webkit-scrollbar-thumb {
+  background: #4b5563;
+  border-radius: 4px;
+}
+
+::-webkit-scrollbar-thumb:hover {
+  background: #6b7280;
+}
+
+/* Message content */
+.message-content {
+  max-width: none;
+  color: #f3f4f6; /* text-gray-100 */
+}
+
+.message-content pre {
+  background: #1f2937; /* bg-gray-800 */
+  border-radius: 0.5rem;
+  padding: 1rem;
+  overflow-x: auto;
+}
+
+.message-content code {
+  background: #1f2937; /* bg-gray-800 */
+  padding: 0.125rem 0.375rem;
+  border-radius: 0.25rem;
+  font-size: 0.875rem;
+}
+
+.message-content pre code {
+  background: transparent;
+  padding: 0;
+}
+
+/* Typing indicator */
+.typing-indicator {
+  display: flex;
+  gap: 4px;
+}
+
+.typing-indicator span {
+  width: 8px;
+  height: 8px;
+  background: #6b7280;
+  border-radius: 50%;
+  animation: typing 1.4s infinite ease-in-out;
+}
+
+.typing-indicator span:nth-child(1) {
+  animation-delay: 0s;
+}
+
+.typing-indicator span:nth-child(2) {
+  animation-delay: 0.2s;
+}
+
+.typing-indicator span:nth-child(3) {
+  animation-delay: 0.4s;
+}
+
+@keyframes typing {
+  0%,
+  80%,
+  100% {
+    transform: scale(1);
+    opacity: 0.5;
+  }
+  40% {
+    transform: scale(1.2);
+    opacity: 1;
+  }
+}
+
+/* bg-gray-850 custom color */
+.bg-gray-850 {
+  background-color: #1a1f2a;
+}