Added support for SalamandraTA 7B Instruct ACT

[xixianliao]

This PR adds support for the salamandraTA-7b-instruct-ACT model, which follows the existing salamandra_instruct model type. The model has been fine-tuned on domain-specific data provided by the Agència Catalana de Turisme (ACT), and is currently private and accessible only to ACT clients. Usage is the same as for other models of type salamandra_instruct, and we will provide a separate user manual specifically for ACT users.

The small changes are:

• Added the new model checkpoint to the configuration.
• Added Russian (ru) as a supported language.
• Modified the loading logic to support downloading the model from Hugging Face and running in offline mode.

To run the model locally, it must first be downloaded and made available in a local models directory. The Docker container can then be launched using:
-docker run -p 8000:8000 \ -e HF_HUB_OFFLINE=True \ -v ./models:/app/models \ projecteaina/mt-api:latest \ --load MULTI-MULTI-salamandra_instruct_act

Sending a request to this model follows the same format as previous models. For example:
curl --location --request POST 'http://0.0.0.0:8000/api/v1/translate' --header 'Content-Type: application/json' --data-raw '{"src":"ca", "tgt":"es", "text":"c'\''Això és una prova."}'

[jatserias]

LGTM, consider moving the model to BSC-LT (private) for simplicity

[jatserias]

you may need to fix unit test as ru is not expected

[xixianliao]

LGTM, consider moving the model to BSC-LT (private) for simplicity

The model is now on BSC-LT as a private repository.

you may need to fix unit test as ru is not expected

"ru" added in test_api_translate.py.