Remove everything specific to a Gitea deployment (closes #209)

Delete the Gitea compose setup, its document, its two scripts and their
make targets. Drop the Core Rule Set exclusions written for Gitea: the
ten query parameters skipped by rules 930120, 932160 and 932260, and the
gitea_flash and redirect_to cookies. The remaining changes are
renumbered, five in all. Documents and tests use neutral examples.

Model: opus-5-5

internal/servewaf/alerts_test.go

@@ -18,7 +18,7 @@ const (
 	alertWebhookURL = "SWWAF_ALERT_WEBHOOK_URL"
 	alertMaxPerHour = "SWWAF_ALERT_MAX_PER_HOUR"
 	// alertInstance is the instance every alert of these tests gives.
-	alertInstance = "fsn1app1/gitea"
+	alertInstance = "fsn1app1/blog"
 )
 
 func TestBanForABrokenLimitRaisesABanAlertWithItsNotes(t *testing.T) {