Remove what is about deploying behind Gitea (closes #209)

Delete the Gitea compose setup, its document, its two scripts and their
make targets. Documents and tests no longer use Gitea as the example
deployment. The Core Rule Set exclusions for Gitea's false positives in
internal/waf stay, with their comments and tests.

Model: opus-5-5

Makefile

@@ -1,13 +1,11 @@
 .PHONY: bootstrap setup test lint fmt fmt-check tidy check docker hooks build \
-	run example-app gitea-requests gitea-setup
+	run example-app
 
 # Makefile targets are thin shims; the implementations live in script/
 # per the scripts-to-rule-them-all pattern (see the Entrypoints section
 # of README.md). tidy writes go.mod and go.sum as `go mod tidy` does,
 # which test checks. build and run are for working on the code by hand;
-# example-app checks the image with an app built on it; gitea-requests
-# reports the gitea requests the Core Rule Set refuses at the defaults;
-# gitea-setup checks the setup in deploy/gitea.
+# example-app checks the image with an app built on it.
 
 bootstrap:
 	@script/bootstrap
@@ -47,9 +45,3 @@ run:
 
 example-app:
 	@script/example-app
-
-gitea-requests:
-	@script/gitea-requests
-
-gitea-setup:
-	@script/gitea-setup