feat: 对话列表支持分页、收藏、置顶

收藏(is_favorite)/置顶(is_pinned)作为布尔标记存入对话已有 metadata，
复用现有 PATCH /api/threads/{id} 与 search 往返，无需后端改动与迁移。

- hooks: 新增 useUpdateThreadMetadata + useToggleThreadPin/Favorite
- utils: 新增 isThreadPinned/isThreadFavorite/sortThreadsPinnedFirst
- 侧边栏: 置顶优先排序 + 下拉菜单收藏/置顶项 + 置顶图标
- 对话页: 置顶区 + 全部/收藏过滤 + 页码翻页(每页20) + 行内收藏/置顶按钮
- i18n: zh-CN/en-US/types 新增相关文案

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -621,15 +621,15 @@ export function useThreadStream({
           lockThreadRagMode(threadId);
         }
 
-        const mergedContext = {
-          ...context,
-          ...extraContext,
-        };
-
-        await thread.submit(
-          {
-            messages: [
-              {
+        const mergedContext = {
+          ...context,
+          ...extraContext,
+        };
+
+        await thread.submit(
+          {
+            messages: [
+              {
                 type: "human",
                 content: [
                   {
@@ -647,33 +647,33 @@ export function useThreadStream({
               },
             ],
           },
-          {
-            threadId: threadId,
-            streamSubgraphs: true,
-            streamResumable: true,
-            config: {
-              recursion_limit: 1000,
-            },
-            context: {
-              ...mergedContext,
-              thinking_enabled: mergedContext.mode !== "flash",
-              is_plan_mode:
-                mergedContext.mode === "pro" || mergedContext.mode === "ultra",
-              subagent_enabled: mergedContext.mode === "ultra",
-              reasoning_effort:
-                mergedContext.reasoning_effort ??
-                (mergedContext.mode === "ultra"
-                  ? "high"
-                  : mergedContext.mode === "pro"
-                    ? "medium"
-                    : mergedContext.mode === "thinking"
-                      ? "low"
-                      : undefined),
-              memory_injection_enabled:
-                mergedContext.memory_injection_enabled ?? true,
-              rag_mode_enabled: ragModeEnabled,
-              thread_id: threadId,
-            },
+          {
+            threadId: threadId,
+            streamSubgraphs: true,
+            streamResumable: true,
+            config: {
+              recursion_limit: 1000,
+            },
+            context: {
+              ...mergedContext,
+              thinking_enabled: mergedContext.mode !== "flash",
+              is_plan_mode:
+                mergedContext.mode === "pro" || mergedContext.mode === "ultra",
+              subagent_enabled: mergedContext.mode === "ultra",
+              reasoning_effort:
+                mergedContext.reasoning_effort ??
+                (mergedContext.mode === "ultra"
+                  ? "high"
+                  : mergedContext.mode === "pro"
+                    ? "medium"
+                    : mergedContext.mode === "thinking"
+                      ? "low"
+                      : undefined),
+              memory_injection_enabled:
+                mergedContext.memory_injection_enabled ?? true,
+              rag_mode_enabled: ragModeEnabled,
+              thread_id: threadId,
+            },
           },
         );
         void queryClient.invalidateQueries({ queryKey: ["threads", "search"] });
@@ -853,6 +853,86 @@ export function useDeleteMessage() {
   });
 }
 
+/**
+ * Merge metadata into a conversation's record via the Gateway
+ * `PATCH /api/threads/{id}` route. Used to persist per-conversation flags such
+ * as `is_pinned` (置顶) and `is_favorite` (收藏) — a conversation belongs to a
+ * single user, so these live directly on the thread metadata (no join table).
+ * Updates the `["threads", "search"]` cache optimistically so the UI reflects
+ * the toggle immediately, mirroring `useRenameThread`.
+ */
+export function useUpdateThreadMetadata() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: async ({
+      threadId,
+      metadata,
+    }: {
+      threadId: string;
+      metadata: Record<string, unknown>;
+    }) => {
+      const response = await apiFetch(
+        `${getBackendBaseURL()}/api/threads/${encodeURIComponent(threadId)}`,
+        {
+          method: "PATCH",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ metadata }),
+        },
+      );
+      if (!response.ok) {
+        const error = await response
+          .json()
+          .catch(() => ({ detail: "更新对话失败。" }));
+        throw new Error(error.detail ?? "更新对话失败。");
+      }
+    },
+    onSuccess(_, { threadId, metadata }) {
+      queryClient.setQueriesData(
+        {
+          queryKey: ["threads", "search"],
+          exact: false,
+        },
+        (oldData: Array<AgentThread> | undefined) => {
+          if (oldData == null) {
+            return oldData;
+          }
+          return oldData.map((t) =>
+            t.thread_id === threadId
+              ? {
+                  ...t,
+                  metadata: {
+                    ...(t.metadata as Record<string, unknown> | null),
+                    ...metadata,
+                  },
+                }
+              : t,
+          );
+        },
+      );
+    },
+  });
+}
+
+/** Toggle a conversation's pinned (置顶) flag. */
+export function useToggleThreadPin() {
+  const { mutate, ...rest } = useUpdateThreadMetadata();
+  return {
+    ...rest,
+    toggle: (threadId: string, pinned: boolean) =>
+      mutate({ threadId, metadata: { is_pinned: pinned } }),
+  };
+}
+
+/** Toggle a conversation's favorite (收藏) flag. */
+export function useToggleThreadFavorite() {
+  const { mutate, ...rest } = useUpdateThreadMetadata();
+  return {
+    ...rest,
+    toggle: (threadId: string, favorite: boolean) =>
+      mutate({ threadId, metadata: { is_favorite: favorite } }),
+  };
+}
+
 export function useRenameThread() {
   const queryClient = useQueryClient();
   const apiClient = getAPIClient();