fix: Forgejo compose template missing INSTALL_LOCK — API returns 404 until manual install (#634)

Add FORGEJO__security__INSTALL_LOCK: "true" to the forgejo service
environment in generate_compose(). Without this, Forgejo starts in
install-wizard mode and the API returns 404 for all endpoints.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bin/disinto

@@ -167,6 +167,7 @@ services:
       FORGEJO__database__DB_TYPE: sqlite3
       FORGEJO__server__ROOT_URL: http://forgejo:3000/
       FORGEJO__server__HTTP_PORT: "3000"
+      FORGEJO__security__INSTALL_LOCK: "true"
       FORGEJO__service__DISABLE_REGISTRATION: "true"
     networks:
       - disinto-net