feat: Day 8-9 - Project Management API completed

Backend:
- Create project routes (GET, POST, PUT, DELETE)
- Implement projectController with CRUD operations
- Create projectService for database operations
- Add validation middleware for request validation
- Update Prisma schema (add background, researchType, deletedAt fields)
- Implement soft delete for projects

Frontend:
- Create projectApi service module
- Update useProjectStore with fetchProjects and loading state
- Connect ProjectSelector to real API with loading indicator
- Connect CreateProjectDialog to real API with error handling
- Connect EditProjectDialog to real API with loading state
- Add comprehensive error handling and user feedback

Build: Both frontend and backend build successfully

frontend/src/api/projectApi.ts

@@ -0,0 +1,57 @@
+import request from './request';
+import type { Project } from '../stores/useProjectStore';
+
+export interface ApiResponse<T = any> {
+  success: boolean;
+  data?: T;
+  message?: string;
+  error?: string;
+}
+
+export interface CreateProjectRequest {
+  name: string;
+  background: string;
+  researchType: 'observational' | 'interventional';
+}
+
+export interface UpdateProjectRequest {
+  name?: string;
+  background?: string;
+  researchType?: 'observational' | 'interventional';
+}
+
+export const projectApi = {
+  // 获取项目列表
+  getProjects: async (): Promise<ApiResponse<Project[]>> => {
+    const response = await request.get('/projects');
+    return response.data;
+  },
+
+  // 获取单个项目详情
+  getProjectById: async (id: string): Promise<ApiResponse<Project>> => {
+    const response = await request.get(`/projects/${id}`);
+    return response.data;
+  },
+
+  // 创建项目
+  createProject: async (data: CreateProjectRequest): Promise<ApiResponse<Project>> => {
+    const response = await request.post('/projects', data);
+    return response.data;
+  },
+
+  // 更新项目
+  updateProject: async (
+    id: string,
+    data: UpdateProjectRequest
+  ): Promise<ApiResponse<Project>> => {
+    const response = await request.put(`/projects/${id}`, data);
+    return response.data;
+  },
+
+  // 删除项目
+  deleteProject: async (id: string): Promise<ApiResponse> => {
+    const response = await request.delete(`/projects/${id}`);
+    return response.data;
+  },
+};
+