feat(server): MinIO/S3 对象存储兼容（F21）

- 新增 storage 抽象：local 与 s3: 前缀兼容（不改 schema）
- invoice-pool 上传/预览/ocr 读取适配 S3/MinIO
- trialrun compose 增加 minio profile + env 示例与 runbook 指引
- 更新 README 与 v3 CSV 状态推进

server/src/config.js

@@ -50,6 +50,13 @@ function getConfig() {
 
     appTimezone: process.env.APP_TIMEZONE ?? "Asia/Shanghai",
     storageDir: path.resolve(serverRoot, storageDir),
+    storageDriver: process.env.STORAGE_DRIVER ?? "local",
+    s3Endpoint: process.env.S3_ENDPOINT ?? "",
+    s3Region: process.env.S3_REGION ?? "us-east-1",
+    s3Bucket: process.env.S3_BUCKET ?? "",
+    s3AccessKeyId: process.env.S3_ACCESS_KEY_ID ?? "",
+    s3SecretAccessKey: process.env.S3_SECRET_ACCESS_KEY ?? "",
+    s3ForcePathStyle: process.env.S3_FORCE_PATH_STYLE === "true",
     serveClientDist: process.env.SERVE_CLIENT_DIST === "true",
     clientDistDir: path.resolve(serverRoot, clientDistDir),
     signedUrlTtlSeconds: Number(process.env.SIGNED_URL_TTL_SECONDS ?? 600),