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/requestlog_test.go

@@ -19,7 +19,7 @@ const (
 	// requestIDHeader carries the request's id.
 	requestIDHeader = "X-Request-ID"
 	// instance is the SWWAF_INSTANCE_NAME a test sets.
-	instance = "fsn1app1/gitea"
+	instance = "fsn1app1/blog"
 	// ipv6Client is a client on IPv6, and ipv6Group the netblock the rate
 	// limits count it as.
 	ipv6Client = "2001:db8::7"