fix: register translate task in celery_worker and add setting metadata

- Import translate_to_default_language in celery_worker.py
- Add default_document_language to SETTING_METADATA in settings_service.py

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/celery_worker.py

@@ -39,6 +39,7 @@ from app.tasks.refine_text_with_gpt import refine_text_with_gpt  # noqa: F401
 from app.tasks.rotate_pdf_pages import rotate_pdf_pages  # noqa: F401
 from app.tasks.send_to_all import send_to_all_destinations  # noqa: F401
 from app.tasks.subscription_tasks import apply_pending_subscription_changes_all  # noqa: F401
+from app.tasks.translate_to_default_language import translate_to_default_language  # noqa: F401
 
 # Import new send tasks
 from app.tasks.upload_to_dropbox import upload_to_dropbox  # noqa: F401

app/utils/settings_service.py

@@ -522,6 +522,19 @@ SETTING_METADATA = {
         "required": False,
         "restart_required": False,
     },
+    # Document Translation
+    "default_document_language": {
+        "category": "AI Services",
+        "description": (
+            "ISO 639-1 language code for the default document translation target "
+            "(e.g. 'en', 'de', 'fr'). Documents whose detected language differs "
+            "are automatically translated into this language after processing."
+        ),
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
     # OCR Engine Configuration
     "ocr_providers": {
         "category": "OCR Engines",