refactor: prefix Mi for all entities (misskey-dev#11719) (MisskeyIO#160)

cheery-pick from misskey-dev@792622aeadf3e36d50cddec3c64b2ff0105ea927

packages/backend/src/models/entities/Instance.ts

@@ -6,8 +6,8 @@
 import { Entity, PrimaryColumn, Index, Column } from 'typeorm';
 import { id } from '../id.js';
 
-@Entity()
-export class Instance {
+@Entity('instance')
+export class MiInstance {
 	@PrimaryColumn(id())
 	public id: string;