chore: synchronize code and database schema (#8577)

* chore: remove default null

null is always the default value if a table column is nullable, and typeorm's
@Column only accepts strings for default.

* chore: synchronize code with database schema

* chore: sync generated migrations with code

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

@@ -17,7 +17,6 @@ export class Muting {
 	@Index()
 	@Column('timestamp with time zone', {
 		nullable: true,
-		default: null,
 	})
 	public expiresAt: Date | null;