feat: add configurable vision focus prompts

frontend/src/lib/api.ts

@@ -327,6 +327,7 @@ export type Assistant = {
   startup: StartupConfig;
   visionEnabled: boolean;
   visionModelResourceId: string | null;
+  visionFocusPrompt: string;
   modelResourceIds: Partial<Record<ModelType, string>>;
   knowledgeBaseId: string | null;
   knowledgeRetrievalConfig: KnowledgeRetrievalConfig;
@@ -371,6 +372,14 @@ export const assistantsApi = {
   // 服务端整行复制(含真 key,密钥不经浏览器)
   duplicate: (id: string) =>
     request<Assistant>(`/api/assistants/${id}/duplicate`, { method: "POST" }),
+  generateVisionFocus: (body: {
+    sourcePrompt: string;
+    modelResourceId: string;
+  }) =>
+    request<{ focusPrompt: string }>("/api/assistants/vision-focus/generate", {
+      method: "POST",
+      body: JSON.stringify(body),
+    }),
   remove: (id: string) =>
     request<{ ok: boolean }>(`/api/assistants/${id}`, { method: "DELETE" }),
 };