Strip advisory identifiers (GHSA-*) from describe blocks, test
docblocks, and inline comments. Replace with plain descriptive
labels. Also clean up FQCNs to use imported class names and minor
style fixes (string concatenation spacing).
Reuse the existing SafeWebhookUrl rule on the S3 Storage endpoint field so
the create and edit forms go through the same URL-normalization path as
webhook settings. Adds a matching guard inside S3Storage::testConnection()
so background callers (scheduled backups, database import reuse) also
validate the endpoint before building the S3 client.
Also fixes an IPv6-bracket edge case in SafeWebhookUrl so `http://[::1]`
style hosts are normalized before the filter_var IP check — the rule's
own loopback test was already asserting this behaviour.
