fix(signal): remove redundant db_session.commit() in create_signal_instance

[whitdog47]

This PR fixes a potential transaction issue by removing a redundant commit in the create_signal_instance function, since commit behavior is already managed by the nested context manager.

Context:

This context manager calls create_signal_instance

for message in response["Messages"]:
    ...
                    with db_session.begin_nested():
                        signal_instance = signal_service.create_signal_instance(
                            db_session=db_session,
                            signal_instance_in=signal_instance_in,
                        )

but at the end of that function we commit the transaction

def create_signal_instance(*, db_session: Session, signal_instance_in: SignalInstanceCreate):
    ...
    db_session.commit()

    return signal_instance 

but with being_nested(), the committing should be handled by the context manager so this commit() leaves the session in an undefined state and could close the transaction.

[Copilot]

Pull Request Overview

This PR fixes a potential transaction issue by removing a redundant commit in the create_signal_instance function, since commit behavior is already managed by the nested context manager.

• Removes the extra db_session.commit() call in create_signal_instance.
• Ensures that the transaction remains valid under begin_nested() usage.

Comments suppressed due to low confidence (1)

src/dispatch/signal/service.py:195

• The removal of the db_session.commit() call is necessary because the commit is already managed by the context manager using begin_nested(), avoiding potential undefined session states.

db_session.commit()