refactor(chat): extract chat page into separate components

将AI聊天页面拆分为独立的组件模块，包括侧边栏、导航栏、消息列表和输入框，提升代码可维护性

frontend/web/src/views/module_ai/chat/components/FaChatMessages.vue

@@ -18,6 +18,7 @@
 <script setup lang="ts">
 import { ref, nextTick, watch } from "vue";
 import WelcomeScreen from "./FaWelcomeScreen.vue";
+import FaMessageItem from "./FaMessageItem.vue";
 import type { ChatMessage } from "../types";
 
 interface Props {

frontend/web/src/views/module_ai/chat/index.vue

@@ -55,6 +55,10 @@ import { ElMessage, ElMessageBox } from "element-plus";
 import AiChatAPI, { ChatSession } from "@/api/module_ai/chat";
 import { Auth } from "@utils/auth";
 import type { ChatMessage, UploadedFile } from "./types";
+import FaSidebar from "./components/FaSidebar.vue";
+import FaChatNavbar from "./components/FaChatNavbar.vue";
+import FaChatMessages from "./components/FaChatMessages.vue";
+import FaChatInput from "./components/FaChatInput.vue";
 
 // 状态
 const messages = ref<ChatMessage[]>([]);