Refactor: migrate pdf_parser.py to golang (#16323)

### What problem does this PR solve?

Http API based on onnx model.
pdf_parser.py to golang

### Type of change

- [x] Refactoring

docker/README.md

@@ -89,6 +89,17 @@ The [.env](./.env) file contains important environment variables for Docker.
 >   - `RAGFLOW_IMAGE=swr.cn-north-4.myhuaweicloud.com/infiniflow/ragflow:nightly` or,
 >   - `RAGFLOW_IMAGE=registry.cn-hangzhou.aliyuncs.com/infiniflow/ragflow:nightly`.
 
+### DeepDoc Vision Service (OSS)
+
+- `DEEPDOC_URL`  
+  URL for the deepdoc vision API serving DLA (layout analysis), OCR (text detection/recognition), and TSR (table structure recognition). The `deepdoc` service in `docker-compose.yml` provides this endpoint. Defaults to `http://deepdoc:9390`. When unset, the parser falls back to inline ONNX Runtime inference.
+
+  > The OSS deepdoc service runs on CPU using ONNX Runtime models. No GPU required.  
+  > API endpoints: `GET /health`, `GET /model`, `POST /predict/dla`, `POST /predict/tsr`, `POST /predict/ocr`.
+
+- `DEEPDOC_IMAGE`  
+  Docker image for the OSS deepdoc service. Defaults to `infiniflow/deepdoc_oss:latest`.
+
 ### Timezone
 
 - `TZ`  
@@ -167,6 +178,13 @@ Before setting `DOC_ENGINE=oceanbase`, make sure the host OS allows the file des
   - `host`: The API server's IP address inside the Docker container. Defaults to `0.0.0.0`.
   - `port`: The API server's serving port inside the Docker container. Defaults to `9380`.
 
+- `deepdoc`  
+  The OSS DeepDoc vision service provides DLA, OCR, and TSR inference via ONNX Runtime.
+  Defined in `docker-compose.yml`, it is started automatically as a dependency of `ragflow-cpu` and `ragflow-gpu`.
+  - `image`: Docker image. Defaults to `infiniflow/deepdoc_oss:latest`.
+  - `port`: Serving port inside the container. Defaults to `9390`.
+  - Health check: `curl -f http://localhost:9390/health` every 10s.
+
 - `mysql`
   - `name`: The MySQL database name. Defaults to `rag_flow`.
   - `user`: The username for MySQL.