[Feat] Add PaddleOCRLoader for local OCR LangChain integration

[Ihebdhouibi]

Add PaddleOCRLoader that wraps the local PaddleOCR library (PP-OCRv5 and PP-StructureV3) to produce LangChain Document objects.

New files:

• langchain_paddleocr/document_loaders/paddleocr.py: PaddleOCRLoader, PaddleOCRConfig dataclass, custom exception hierarchy

• tests/unit_tests/document_loaders/test_paddleocr_loader.py: 29 unit tests

• tests/integration_tests/document_loaders/test_paddleocr_loader.py: Integration tests

Modified files:

• langchain_paddleocr/init.py: Add PaddleOCRLoader export (lazy import for PaddleOCRVLLoader)

• langchain_paddleocr/document_loaders/init.py: Same

• README.md / README_cn.md: Add PaddleOCRLoader usage docs

[paddle-bot]

Thanks for your contribution!

[Bobholamovic]

Thank you very much for your contribution! I'd like to clarify a point to avoid any potential confusion: within the project, PaddleOCR typically refers to the general OCR capability, whereas the PP-Structure series is intended for more complex document parsing. Since they differ quite a bit in terms of scope and design goals, it might be better to keep them separated. From an architectural perspective, I would gently suggest not combining them into a single class, so that the design remains clearer and easier to maintain.

[Ihebdhouibi]

Thank you very much for your contribution! I'd like to clarify a point to avoid any potential confusion: within the project, PaddleOCR typically refers to the general OCR capability, whereas the PP-Structure series is intended for more complex document parsing. Since they differ quite a bit in terms of scope and design goals, it might be better to keep them separated. From an architectural perspective, I would gently suggest not combining them into a single class, so that the design remains clearer and easier to maintain.

Absolutely spot on, I'll fix that and update the PR

[Ihebdhouibi]

@Bobholamovic Changes done as required, pending review