feat(auth): 添加认证模块和图片批注功能（项目初始化）

- 实现用户登录、登出、密码修改等认证功能
- 添加会话管理和权限控制中间件
- 创建图片批注组件和相关API路由
- 实现批注的增删改查功能
- 添加Docker和Git忽略配置文件
- 创建系统架构文档和开发约定说明
- 集成认证模块到前端应用路由中

api/upload.ts

@@ -0,0 +1,51 @@
+/**
+ * multer 文件上传配置
+ */
+import multer from 'multer';
+import path from 'path';
+import fs from 'fs';
+import { fileURLToPath } from 'url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+const uploadsDir = path.resolve(__dirname, '..', 'uploads');
+if (!fs.existsSync(uploadsDir)) {
+  fs.mkdirSync(uploadsDir, { recursive: true });
+}
+
+const storage = multer.diskStorage({
+  destination: (_req, _file, cb) => {
+    cb(null, uploadsDir);
+  },
+  filename: (_req, file, cb) => {
+    const ext = path.extname(file.originalname).toLowerCase() || '.jpg';
+    const unique = `${Date.now()}_${Math.round(Math.random() * 1e6)}${ext}`;
+    cb(null, unique);
+  },
+});
+
+const allowedMime = new Set([
+  'image/jpeg',
+  'image/png',
+  'image/gif',
+  'image/webp',
+  'image/avif',
+]);
+
+export const upload = multer({
+  storage,
+  limits: {
+    fileSize: 20 * 1024 * 1024, // 20MB / 单图
+    files: 30, // 最多 30 张
+  },
+  fileFilter: (_req, file, cb) => {
+    if (allowedMime.has(file.mimetype)) {
+      cb(null, true);
+    } else {
+      cb(new Error(`不支持的文件类型: ${file.mimetype}`));
+    }
+  },
+});
+
+export const UPLOADS_DIR = uploadsDir;