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/state/state_test.go

@@ -143,7 +143,7 @@ const filledAlertsJSON = `{
     "waiting": {
         "webhook": [
             {
-                "instance": "fsn1app1/gitea",
+                "instance": "fsn1app1/blog",
                 "time": "2026-10-06T00:00:00Z",
                 "event": "ban",
                 "client": "203.0.113.9",
@@ -158,7 +158,7 @@ const filledAlertsJSON = `{
                 "suppressed_repeats": 0
             },
             {
-                "instance": "fsn1app1/gitea",
+                "instance": "fsn1app1/blog",
                 "time": "2026-10-06T00:00:00Z",
                 "event": "file_error",
                 "client": "",
@@ -1721,7 +1721,7 @@ func newParams(dir string) state.Params {
 		Events:     alerts.Events(),
 		Cooldown:   15 * time.Minute,
 		MaxPerHour: 2,
-		Instance:   "fsn1app1/gitea",
+		Instance:   "fsn1app1/blog",
 		Now:        midnight,
 	})