fix: propagate ctx to gtfstidy subprocess

[ashnaaseth2325-oss]

SUMMARY

This PR fixes a context propagation issue in the GTFS tidy pipeline where subprocesses could not be canceled, leading to hangs during shutdown or timeout. It updates tidyGTFSData to accept a context.Context and uses exec.CommandContext instead of exec.Command.

Primary changes are in internal/gtfs/tidy.go, with call-site updates in internal/gtfs/static.go and test adjustments in internal/gtfs/tidy_test.go.

---

FIX

// Before
func tidyGTFSData(inputZip []byte, logger *slog.Logger) ([]byte, error) {
    cmd := exec.Command(gtfstidyPath, "-OscRCSmeD", "-o", outputZipPath, pristineZipPath)
}

// After
func tidyGTFSData(ctx context.Context, inputZip []byte, logger *slog.Logger) ([]byte, error) {
    cmd := exec.CommandContext(ctx, gtfstidyPath, "-OscRCSmeD", "-o", outputZipPath, pristineZipPath)
}

---

VERIFICATION

Tested by enabling GTFS tidy, triggering a feed update, and sending a SIGTERM while the tidy process was running. The service now shuts down cleanly without hanging, and the subprocess exits immediately on cancellation. Builds and existing tests pass with no regressions.

[ashnaaseth2325-oss]

Hi @aaronbrethorst
Kindly you please review the PR.
Thanks!

[ashnaaseth2325-oss]

Hello @aaronbrethorst
Just a quick follow-up. Would appreciate your feedback when you have a moment.
Thanks!