fix: Add explicit commit/rollback in PostgreSQL context manager exit

- On successful execution (no exception): explicitly commit before closing
- On exception: explicitly rollback before closing
- Add try-except to handle commit/rollback failures gracefully

This ensures that all inserted data is committed to the database
when the context manager exits. Previously, commits were only done
per-batch in insert_batch(), but the final context exit wasn't
ensuring a final commit.

Fixes: Data not appearing in PostgreSQL after migration completes

src/connectors/postgres_connector.py

@@ -49,6 +49,18 @@ class PostgreSQLConnector:
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         """Context manager exit."""
+        if exc_type is None:
+            # No exception, commit before closing
+            try:
+                self.connection.commit()
+            except Exception as e:
+                logger.warning(f"Failed to commit on exit: {e}")
+        else:
+            # Exception occurred, rollback
+            try:
+                self.connection.rollback()
+            except Exception as e:
+                logger.warning(f"Failed to rollback on exit: {e}")
         self.disconnect()
 
     def execute(self, query: str, params: Optional[tuple] = None) -> None: