feat: 数据集下载鉴权、MinIO 发布与数据库兼容增强

- 数据集下载接口鉴权：单文件直接返回、多文件打包 ZIP，前端统一走请求客户端携带 Token
- 预检/同步支持 MinIO 对象补建与资源副本记录，兼容接入 MinIO 前的历史数据集
- create_dataset 增加名称重复校验，软删记录释放名称并保留墓碑
- 数据处理发布结果支持写入 MinIO storage_objects 并关联 dataset_file
- 数据存储根目录支持 YG_FT_DATA_ROOT 环境变量
- SQL 迁移兼容旧版 approval_steps / retention_policies / data_process_results
- 训练日志图表按曲线独立过滤缺失采样点

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

backend/app/db/platform_store.py

@@ -1607,7 +1607,24 @@ class PlatformStore:
 
     def create_dataset(self, payload: dict[str, Any]) -> dict[str, Any]:
         dataset_id = payload.get("id") or new_id("ds")
+        name = str(payload.get("name") or "").strip()
+        if not name:
+            raise ValueError("dataset name is required")
         with self.connect() as conn:
+            existing = conn.execute(
+                "SELECT id, deleted_at FROM datasets WHERE name=?",
+                (name,),
+            ).fetchone()
+            if existing and not existing.get("deleted_at"):
+                raise ValueError(f"dataset name already exists: {name}")
+            # Soft-deleted records remain in the database for audit/history and
+            # still participate in the legacy unique constraint. Free the name
+            # while retaining a traceable tombstone before creating the new row.
+            if existing:
+                conn.execute(
+                    "UPDATE datasets SET name=? WHERE id=?",
+                    (f"{name}__deleted__{existing['id']}", existing["id"]),
+                )
             conn.execute(
                 """
                 INSERT INTO datasets
@@ -1616,7 +1633,7 @@ class PlatformStore:
                 """,
                 (
                     dataset_id,
-                    payload["name"],
+                    name,
                     payload.get("type", "train"),
                     payload.get("storage_type", "local"),
                     payload.get("source", "upload"),
@@ -2965,6 +2982,27 @@ class PlatformStore:
             ).fetchone()
             return dict(row)
 
+    def link_dataset_file_storage_object(self, file_id: str, storage_object_id: str) -> None:
+        """Link an uploaded dataset file to its canonical MinIO object."""
+        with self.connect() as conn:
+            conn.execute(
+                """
+                UPDATE dataset_files
+                SET storage_object_id=?
+                WHERE id=?
+                """,
+                (storage_object_id, file_id),
+            )
+            row = conn.execute(
+                "SELECT dataset_id FROM dataset_files WHERE id=?",
+                (file_id,),
+            ).fetchone()
+            if row:
+                conn.execute(
+                    "UPDATE datasets SET storage_type='minio' WHERE id=?",
+                    (row["dataset_id"],),
+                )
+
     def storage_objects_for_resource(self, resource_type: str, resource_id: str) -> list[dict[str, Any]]:
         with self.connect() as conn:
             rows = conn.execute(