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

deepdoc/server/endpoints/dla_endpoint.py

@@ -0,0 +1,43 @@
+"""DLA LitServe endpoint."""
+
+import logging
+
+import litserve as ls
+
+from deepdoc.server.adapters.dla_adapter import DLAAdapter
+
+logger = logging.getLogger(__name__)
+
+
+class DLAEndpoint(ls.LitAPI):
+    """Document Layout Analysis endpoint at /predict/dla."""
+
+    def __init__(self, model_dir: str, thr: float = 0.2):
+        super().__init__()
+        self.api_path = "/predict/dla"
+        self.model_dir = model_dir
+        self.thr = thr
+        self.adapter: DLAAdapter | None = None
+
+    def setup(self, device):
+        self.adapter = DLAAdapter(model_dir=self.model_dir, thr=self.thr)
+        self.adapter.load()
+        logger.info("DLA model loaded")
+
+    def decode_request(self, request):
+        # Handle both Starlette UploadFile (old) and FormData (Starlette >=1.3)
+        if hasattr(request, "file"):
+            data = request.file.read()
+        else:
+            data = request.get("request").file.read()
+        if not data:
+            raise ValueError("Empty request body")
+        if len(data) > 50 * 1024 * 1024:  # 50MB
+            raise ValueError("Image too large")
+        return data
+
+    def predict(self, image_data: bytes):
+        return self.adapter(image_data)
+
+    def encode_response(self, output):
+        return {"bboxes": output}