feat: added configable summary calculation and various improvements

- Replaced direct embedding calls with a utility function across various components to streamline embedding logic.
- Added enable_summary flag to several models and routes to control summary generation behavior.

surfsense_backend/app/indexing_pipeline/document_embedder.py

@@ -1,6 +1,3 @@
-from app.config import config
+from app.utils.document_converters import embed_text
 
-
-def embed_text(text: str) -> list[float]:
-    """Embed a single text string using the configured embedding model."""
-    return config.embedding_model_instance.embed(text)
+__all__ = ["embed_text"]