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/jobs/ocrJob.js

@@ -1,8 +1,7 @@
-const fs = require("node:fs/promises");
-const path = require("node:path");
 const cron = require("node-cron");
 
 const { runOcrForInvoice } = require("../services/ocr");
+const { readFileBuffer } = require("../services/storage");
 
 const OCR_DUPLICATE_ERROR = "duplicate_invoice_code_number";
 
@@ -222,8 +221,10 @@ async function markInvoiceAsFailed(prisma, claimedInvoice, errorMessage, config)
 
 async function processClaimedInvoice(prisma, config, claimedInvoice, workerId, logger) {
   try {
-    const absolutePath = path.resolve(config.storageDir, claimedInvoice.storage_path);
-    const fileBuffer = await fs.readFile(absolutePath);
+    const fileBuffer = await readFileBuffer({
+      config,
+      storagePath: claimedInvoice.storage_path,
+    });
     const imageBase64 = fileBuffer.toString("base64");
 
     const { ocrResultId, normalized } = await getOrCreateOcrResult(