feat: 新增 MinIO 对象存储与算力节点缓存预下载

- 后端新增 storage 模块（minio_store），支持 MinIO 预签名 URL 上传与对象管理
- config 新增 MinIO 及存储等待相关配置项
- 算力节点新增 /compute/cache/prepare 缓存预下载接口（带校验和原子落盘）
- 算力节点健康接口增加存储可用性探针
- SQL 迁移补充资源存储相关表结构
- Docker 新增 minio 服务与后端 minio 配置
- 补充 minio-compute-cache-plan 设计文档

Co-Authored-By: Claude <noreply@anthropic.com>

backend/app/modules/storage/minio_store.py

@@ -0,0 +1,68 @@
+from __future__ import annotations
+
+from datetime import timedelta
+from functools import lru_cache
+from io import BytesIO
+from typing import Any
+
+from minio import Minio
+from minio.error import S3Error
+
+from app.core.config import get_settings
+
+
+class ObjectStorageError(RuntimeError):
+    pass
+
+
+class MinioObjectStorage:
+    def __init__(self) -> None:
+        settings = get_settings()
+        endpoint = settings.minio_endpoint.replace("http://", "").replace("https://", "").rstrip("/")
+        self.client = Minio(endpoint, access_key=settings.minio_access_key, secret_key=settings.minio_secret_key, secure=settings.minio_secure)
+        self.bucket = settings.minio_bucket
+
+    def _ensure_enabled(self) -> None:
+        if not get_settings().minio_enabled:
+            raise ObjectStorageError("MinIO object storage is disabled")
+
+    def ensure_bucket(self) -> None:
+        self._ensure_enabled()
+        try:
+            if not self.client.bucket_exists(self.bucket):
+                self.client.make_bucket(self.bucket)
+        except S3Error as exc:
+            raise ObjectStorageError(str(exc)) from exc
+
+    def presigned_put(self, object_key: str, expires_seconds: int = 3600) -> str:
+        self._ensure_enabled()
+        self.ensure_bucket()
+        return self.client.presigned_put_object(self.bucket, object_key, expires=timedelta(seconds=expires_seconds))
+
+    def presigned_get(self, object_key: str, expires_seconds: int = 3600) -> str:
+        self._ensure_enabled()
+        self.ensure_bucket()
+        return self.client.presigned_get_object(self.bucket, object_key, expires=timedelta(seconds=expires_seconds))
+
+    def stat(self, object_key: str) -> dict[str, Any]:
+        self._ensure_enabled()
+        self.ensure_bucket()
+        try:
+            result = self.client.stat_object(self.bucket, object_key)
+            return {"object_key": object_key, "byte_size": result.size, "etag": result.etag, "last_modified": result.last_modified.isoformat() if result.last_modified else None}
+        except S3Error as exc:
+            raise ObjectStorageError(str(exc)) from exc
+
+    def put_bytes(self, object_key: str, content: bytes, content_type: str = "application/octet-stream") -> dict[str, Any]:
+        self._ensure_enabled()
+        self.ensure_bucket()
+        try:
+            result = self.client.put_object(self.bucket, object_key, BytesIO(content), len(content), content_type=content_type)
+            return {"bucket": self.bucket, "object_key": object_key, "etag": result.etag, "byte_size": len(content)}
+        except S3Error as exc:
+            raise ObjectStorageError(str(exc)) from exc
+
+
+@lru_cache
+def get_object_storage() -> MinioObjectStorage:
+    return MinioObjectStorage()