fix(ocr): use camelCase field names in Pydantic models

Pydantic v2 Field(alias=...) doesn't work with FastAPI as expected.
The Java client sends camelCase (pdfUrl, scriptType, pageNumber).
Use camelCase field names directly instead of aliases.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ocr-service/models.py

@@ -1,20 +1,21 @@
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, ConfigDict
 
 
 class OcrRequest(BaseModel):
-    pdf_url: str = Field(..., alias="pdfUrl")
-    script_type: str = Field("UNKNOWN", alias="scriptType")
+    model_config = ConfigDict(populate_by_name=True)
+
+    pdfUrl: str
+    scriptType: str = "UNKNOWN"
     language: str = "de"
 
 
 class OcrBlock(BaseModel):
-    page_number: int = Field(..., alias="pageNumber")
+    model_config = ConfigDict(populate_by_name=True)
+
+    pageNumber: int
     x: float
     y: float
     width: float
     height: float
     polygon: list[list[float]] | None = None
     text: str
-
-    class Config:
-        populate_by_name = True