Change RoadmapRevision check from hardcoded string to comparing against
the HTTP payload's `after` variable directly, proving the full chain:
HTTP payload `after` → scanner → bridge → job.RoadmapRevision.
Add TestGitoHTTPWebhookDeliveryEnqueuesCreationSyncOnce to prove that a
signed HTTP branch.updated delivery reaches gitoBridgeHTTPAdapter, triggers
the bridge scanner, and enqueues exactly one RoadmapCreationSync job.
Also adds TestGitoHTTPWebhookDeliveryRejectedOnInvalidSignature and
TestGitoHTTPWebhookDeliveryOffTargetIgnored for completeness.
