fix: remove use of ImagePromptTemplate in image handling and adds image utils (#4467)

* remove poetry.lock

* fix: update langchain-core dependency version to 0.3.15

* feat: add functions to convert images to base64 and create data URLs

* refactor: simplify image URL handling by replacing ImagePromptTemplate with create_data_url function

* Fix image URL structure in data schema to use nested dictionary format

* Add unit tests for Data schema message conversion with text and images

* test: add unit tests for image utility functions to validate base64 conversion and data URL creation

* Refactor image URL generation to use `create_data_url` utility function instead of `ImagePromptTemplate`

* Add unit tests for message handling and image processing in schema module

- Introduce fixtures for temporary cache directory and sample image creation.
- Add tests for message creation from human and AI text.
- Implement tests for messages with single and multiple images.
- Include tests for invalid image paths and messages without sender.
- Add message serialization and conversion tests.
- Ensure cleanup of cache directory after tests.

* Use platformdirs to determine cache directory paths in test_schema_message.py

src/backend/base/pyproject.toml

@@ -111,7 +111,7 @@ dependencies = [
     "uvicorn>=0.30.0",
     "gunicorn>=22.0.0",
     "langchain~=0.3.3",
-    "langchain-core~=0.3.10",
+    "langchain-core~=0.3.15",
     "langchainhub~=0.1.15",
     "sqlmodel==0.0.18",
     "loguru>=0.7.1",