enhance: いくつかの設定ファイルの項目をコントロールパネルで設定するように (#16026)

* wip

* Update CHANGELOG.md

* feat: migrate to existing config value (#16030)

* wip

* Update CHANGELOG.md

---------

Co-authored-by: anatawa12 <anatawa12@icloud.com>

packages/backend/src/models/Meta.ts

@@ -680,6 +680,21 @@ export class MiMeta {
 		default: false,
 	})
 	public singleUserMode: boolean;
+
+	@Column('boolean', {
+		default: true,
+	})
+	public proxyRemoteFiles: boolean;
+
+	@Column('boolean', {
+		default: true,
+	})
+	public signToActivityPubGet: boolean;
+
+	@Column('boolean', {
+		default: true,
+	})
+	public allowExternalApRedirect: boolean;
 }
 
 export type SoftwareSuspension = {