GitLab

- Restore Gravatar functionality
- Add new button for "Use Initials"
- Set both buttons to use text-left class
- Update toast property autoClose to duration (wrong library, my bad!)
- Update toast messages to clarify that this isn't "Gravatar" but "avatar"
- Add i18n text to en-US/translation.json

* Tooltips added to show full model name and warning regarding vector storage
* Send toast error and return early if more than a single front slash is detected
* Extend toast duration for model update action
* Add i18n en_US translation
* Remove commented code copied from existing function

Browsers and plugins that spoof canvas data produce corrupt images. In attempt to mitigate:

* Add canvasPixelTest() to test a single pixel and test the RGB values
* Test canvasPixelTest() inside generateInitialsImage() and use default `/user.png` if failure detected
* Call canvasPixelTest() directly within settings to avoid setting an invalid image
* Use toast.error() with 10 second autoClose

* Add config variable RAG_EMBEDDING_MODEL_AUTO_UPDATE to control update behavior
* Add RAG utils embedding_model_get_path() function to output the filesystem path in addition to update of the model using huggingface_hub
* Update and utilize existing RAG functions in main: get_embedding_model() & update_embedding_model()
* Add GUI setting to execute manual update process