feat: license violation protection (#13285)

* spec(frontend): aboutページにリポジトリ・フィードバックのURLを表示させる

Cherry-picked from MisskeyIO#441
Cherry-picked from MisskeyIO#438

* feat: license violation protection

* build: fix typo

* build: fix typo

* fix: farewell to the static type land

* fix: key typo

* fix: import typo

* fix: properly interpret `prominently`

* docs: add disclaimer

* docs: update CHANGELOG

* chore: add gap

---------

Co-authored-by: まっちゃとーにゅ <17376330+u1-liquid@users.noreply.github.com>
Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

packages/backend/src/server/api/endpoints/admin/meta.ts

@@ -429,7 +429,7 @@ export const meta = {
 			},
 			repositoryUrl: {
 				type: 'string',
-				optional: false, nullable: false,
+				optional: false, nullable: true,
 			},
 			summalyProxy: {
 				type: 'string',