[add]: database connection

app/models/batch_results.py

@@ -24,7 +24,7 @@ class BatchResult(db.Model):
 
 
     @classmethod
-    def save_batch(cls, session: Session, batch_number, total_batches, results_df, status="success"):
+    def save_batch(cls, batch_number, total_batches, results_df, status="success"):
         """Save batch results into DB using ORM bulk insert."""
         try:
             results_df["batch_number"] = batch_number
@@ -42,21 +42,21 @@ class BatchResult(db.Model):
                 for row in results_df.to_dict("records")
             ]
 
-            session.bulk_save_objects(records)
-            session.commit()
+            db.session.bulk_save_objects(records)
+            db.session.commit()
             logger.info(f"Saved batch {batch_number} successfully.")
             return True
         except Exception as e:
-            session.rollback()
+            db.session.rollback()
             logger.error(f"Error saving batch {batch_number}: {str(e)}")
             return False
 
     @classmethod
-    def get_batch_status(cls, session: Session, batch_number: int):
+    def get_batch_status(cls, batch_number: int):
         """Return summary info about one batch."""
         try:
             result = (
-                session.query(
+                db.session.query(
                     cls.batch_number,
                     cls.total_batches,
                     cls.processed_at,
@@ -75,11 +75,11 @@ class BatchResult(db.Model):
             return None
 
     @classmethod
-    def get_all_batches(cls, session: Session):
+    def get_all_batches(cls):
         """Return summaries for all batches."""
         try:
             results = (
-                session.query(
+                db.session.query(
                     cls.batch_number,
                     cls.total_batches,
                     cls.processed_at,