新增智能体收藏、定时任务必须生成MD校验、问答时间显示及账号绑定的常用提示词

- 智能体支持从广场收藏到「我的」（新增 agent_favorites 表与收藏/取消收藏接口）
- 定时任务新增「必须生成Markdown文件」开关：注入提示词并校验生成的 .md 文件且正文超过100字，否则记为失败（存于 execution_context，无需迁移）
- 聊天问答展示时间（年月日 时分）：问题在右下角、回答在左下角
- 常用提示词改为与账号绑定（新增 user_custom_prompts 表与 /api/user-prompts 接口），仅在首页输入框上方以居中标签 + 轮播展示，齿轮置于最右侧管理

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend-web/src/core/threads/hooks.ts

@@ -11,6 +11,7 @@ import type { PromptInputMessage } from "@/components/ai-elements/prompt-input";
 import { getAPIClient } from "../api";
 import { apiFetch } from "../api";
 import { getStoredAuth } from "../auth";
+import { rememberAskTime } from "../chat-timestamps";
 import { getBackendBaseURL } from "../config";
 import { useI18n } from "../i18n/hooks";
 import type { FileInMessage } from "../messages/utils";
@@ -378,6 +379,13 @@ export function useThreadStream({
   const [optimisticMessages, setOptimisticMessages] = useState<Message[]>([]);
   const [isUploading, setIsUploading] = useState(false);
   const sendInFlightRef = useRef(false);
+  // Carries the ask time of an in-flight send until the server-assigned human
+  // message id shows up, so we can bind the timestamp to the real id (see the
+  // reconciliation effect below). ``known`` is the set of human ids that
+  // already existed at send time, used to spot the newly-arrived one.
+  const pendingAskTimeRef = useRef<{ ts: string; known: Set<string> } | null>(
+    null,
+  );
   // Track message count before sending so we know when server has responded
   const prevMsgCountRef = useRef(thread.messages.length);
 
@@ -429,6 +437,26 @@ export function useThreadStream({
     }
   }, [thread.messages.length, optimisticMessages.length]);
 
+  // Bind a just-sent question's ask time to the server-assigned human message
+  // id once it appears. Persists to localStorage so the time shows on every
+  // question and survives reloads, independent of the backend echoing it back.
+  useEffect(() => {
+    const pending = pendingAskTimeRef.current;
+    if (!pending) return;
+    for (const message of thread.messages) {
+      if (
+        message.type === "human" &&
+        message.id &&
+        !message.id.startsWith("opt-") &&
+        !pending.known.has(message.id)
+      ) {
+        rememberAskTime(message.id, pending.ts);
+        pendingAskTimeRef.current = null;
+        break;
+      }
+    }
+  }, [thread.messages]);
+
   const sendMessage = useCallback(
     async (
       threadId: string,
@@ -442,6 +470,20 @@ export function useThreadStream({
       sendInFlightRef.current = true;
 
       const text = message.text.trim();
+      // Wall-clock time the question was asked. Stored on the human message so
+      // the chat can show "几点提问" and have it survive a reload (it round-trips
+      // through the checkpoint inside additional_kwargs, same as `files`).
+      const clientTs = new Date().toISOString();
+      // Remember which human messages already exist so the reconciliation
+      // effect can bind ``clientTs`` to the new one once the server returns it.
+      pendingAskTimeRef.current = {
+        ts: clientTs,
+        known: new Set(
+          thread.messages
+            .filter((m) => m.type === "human" && m.id)
+            .map((m) => m.id as string),
+        ),
+      };
 
       // Capture current count before showing optimistic messages
       prevMsgCountRef.current = thread.messages.length;
@@ -458,6 +500,7 @@ export function useThreadStream({
       const hideFromUI = options?.additionalKwargs?.hide_from_ui === true;
       const optimisticAdditionalKwargs = {
         ...options?.additionalKwargs,
+        client_ts: clientTs,
         ...(optimisticFiles.length > 0 ? { files: optimisticFiles } : {}),
       };
 
@@ -535,7 +578,10 @@ export function useThreadStream({
                   return [
                     {
                       ...humanMessage,
-                      additional_kwargs: { files: uploadedFiles },
+                      additional_kwargs: {
+                        ...humanMessage.additional_kwargs,
+                        files: uploadedFiles,
+                      },
                     },
                     ...messages.slice(1),
                   ];
@@ -585,6 +631,7 @@ export function useThreadStream({
                 ],
                 additional_kwargs: {
                   ...options?.additionalKwargs,
+                  client_ts: clientTs,
                   ...(filesForSubmit.length > 0
                     ? { files: filesForSubmit }
                     : {}),