fix: propagate context for cancellable imports

[ashnaaseth2325-oss]

SUMMARY

This PR fixes a context propagation issue in the GTFS import flow that prevented database operations from being cancellable during shutdown. The change ensures the caller’s context.Context is properly passed through instead of being overridden.

Primary changes are in gtfsdb/helpers.go and gtfsdb/client.go, specifically around processAndStoreGTFSDataWithSource and its callers.

---

FIX

// Before 
func (c *Client) processAndStoreGTFSDataWithSource(b []byte, source string) error {
    ctx := context.Background()
}

// After 
func (c *Client) processAndStoreGTFSDataWithSource(ctx context.Context, b []byte, source string) error {
}

---

VERIFICATION

Tested by triggering a GTFS import and sending a SIGTERM while it was still processing. Before this change, the app would hang for minutes waiting for the DB writes to finish. Now, the import cancels immediately and the service shuts down cleanly without delay.

[ashnaaseth2325-oss]

Hello @aaronbrethorst
This change ensures GTFS imports respect the caller’s context, allowing them to be cancelled during shutdown. It helps avoid long-running DB operations blocking a clean and timely exit.