Add conversation history management and API endpoints

- Introduce new database models for conversation sessions, messages, and artifacts to support conversation history tracking.
- Implement API routes for listing conversations and retrieving detailed conversation data, enhancing user interaction with historical records.
- Add a conversation recorder service to persist conversation messages in real-time without disrupting ongoing calls.
- Update the frontend to display conversation history, including filtering and sorting options, improving user experience.
- Enhance the pipeline to integrate conversation history recording seamlessly during interactions.

frontend/src/lib/api.ts

@@ -194,6 +194,63 @@ export const assistantsApi = {
     request<{ ok: boolean }>(`/api/assistants/${id}`, { method: "DELETE" }),
 };
 
+// ---------- 对话历史 ----------
+export type Conversation = {
+  id: string;
+  assistantId: string | null;
+  assistantName: string;
+  channel: string;
+  runtimeMode: string;
+  status: string;
+  messageCount: number;
+  startedAt: string;
+  endedAt: string | null;
+};
+
+export type ConversationMessage = {
+  id: string;
+  sequence: number;
+  role: "user" | "assistant";
+  contentType: string;
+  content: string;
+  occurredAt: string;
+  extra: { interrupted?: boolean; turn_id?: string };
+};
+
+export type ConversationDetail = Conversation & {
+  messages: ConversationMessage[];
+};
+
+export type ConversationList = {
+  items: Conversation[];
+  total: number;
+  page: number;
+  pageSize: number;
+};
+
+export const conversationsApi = {
+  list: (params: {
+    page?: number;
+    pageSize?: number;
+    search?: string;
+    channel?: string;
+    status?: string;
+    sortOrder?: "newest" | "oldest";
+  } = {}) => {
+    const query = new URLSearchParams({
+      page: String(params.page ?? 1),
+      page_size: String(params.pageSize ?? 20),
+      sort_order: params.sortOrder ?? "newest",
+    });
+    if (params.search) query.set("search", params.search);
+    if (params.channel) query.set("channel", params.channel);
+    if (params.status) query.set("status", params.status);
+    return request<ConversationList>(`/api/conversations?${query}`);
+  },
+  get: (id: string) =>
+    request<ConversationDetail>(`/api/conversations/${id}`),
+};
+
 // ---------- 工具 ----------
 export type ToolStatus = "active" | "archived" | "draft";
 export type ToolParameter = {