feat: 管理端专家管理完整CRUD(新增创建和删除)

后端:
- ExpertStore.create_expert: 创建专家(含bcrypt密码哈希)
- ExpertStore.delete_expert: 级联删除(咨询+服务关系+专家)
- POST /admin/experts: 创建专家API
- DELETE /admin/experts/{id}: 删除专家API

前端:
- AdminExperts页面加"新增专家"按钮和创建弹窗
- 创建弹窗含姓名/手机号/密码/分类/职称/简介/专长
- 每个专家卡片加删除按钮,二次确认后删除
- api.ts加adminCreateExpert和adminDeleteExpert方法

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

web2/src/lib/api.ts

@@ -291,6 +291,15 @@ export const api = {
   // ===== 管理后台 =====
   adminListExperts: (status?: string) =>
     request<{ results: Expert[] }>(`/admin/experts${status ? `?status=${status}` : ''}`),
+  adminCreateExpert: (data: {
+    name: string; phone: string; password: string; category: string;
+    title?: string; bio?: string; expertise?: string; avatar_url?: string | null;
+    status?: string;
+  }) => request<{ created: boolean; expert: Expert }>('/admin/experts', {
+    method: 'POST', body: JSON.stringify(data),
+  }),
+  adminDeleteExpert: (expertId: number) =>
+    request<{ deleted: boolean; expert_id: number }>(`/admin/experts/${expertId}`, { method: 'DELETE' }),
   adminUpdateExpertStatus: (expertId: number, status: 'active' | 'inactive') =>
     request<{ updated: boolean; expert_id: number; status: string }>(`/admin/experts/${expertId}/status`, {
       method: 'PATCH', body: JSON.stringify({ status }),