build(release): add giteaurls block so goreleaser targets code.m3ta.dev

GITEA_URL as an env var does nothing in goreleaser v2; the giteaurls
config block is what routes scm releases to the Gitea API. Without it
the publish step fails with: scm releases: invalid URL: "".

.goreleaser.yaml

@@ -3,10 +3,12 @@ version: 2
 project_name: agent-lib
 
 # Releases gehen an die eigene Gitea-Instanz (NICHT GitHub):
-#   GITEA_URL=https://code.m3ta.dev
-#   GITEA_TOKEN=<token mit repository-write>
+#   GITEA_TOKEN=<token mit repository-write> als Umgebungsvariable
 # Repo/Owner werden aus dem origin-Remote abgeleitet
 # (gitea@code.m3ta.dev:m3tam3re/agent-lib.git).
+giteaurls:
+  api: https://code.m3ta.dev/api/v1
+  download: https://code.m3ta.dev
 
 before:
   hooks: