Feat: refine dataflow and initialize dataflow app (#9952)

### What problem does this PR solve?

Refine dataflow and initialize dataflow app.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

rag/flow/chunker/schema.py

@@ -0,0 +1,37 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+from typing import Any, Literal
+
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class ChunkerFromUpstream(BaseModel):
+    created_time: float | None = Field(default=None, alias="_created_time")
+    elapsed_time: float | None = Field(default=None, alias="_elapsed_time")
+
+    name: str
+    blob: bytes
+
+    output_format: Literal["json", "markdown", "text", "html"] | None = Field(default=None)
+
+    json_result: list[dict[str, Any]] | None = Field(default=None, alias="json")
+    markdown_result: str | None = Field(default=None, alias="markdown")
+    text_result: str | None = Field(default=None, alias="text")
+    html_result: str | None = Field(default=None, alias="html")
+
+    model_config = ConfigDict(populate_by_name=True, extra="forbid")
+
+    # def to_dict(self, *, exclude_none: bool = True) -> dict:
+    #     return self.model_dump(by_alias=True, exclude_none=exclude_none)