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/models/Meta.ts

@@ -357,9 +357,9 @@ export class MiMeta {
 	@Column('varchar', {
 		length: 1024,
 		default: 'https://github.com/misskey-dev/misskey',
-		nullable: false,
+		nullable: true,
 	})
-	public repositoryUrl: string;
+	public repositoryUrl: string | null;
 
 	@Column('varchar', {
 		length: 1024,