Gitea should prohibit restoring backup of older schema than currently installed

[CirnoT]

Backup should store its schema version and restore tool should not allow restoring data onto already existing database schema that is of newer version that that of backup.

Such action results in data being migrated without necessary migrations. User should be advised to restore backup on the same version of Gitea as it was made to, and only then upgrade to newer version.

[6543]

@CirnoT we have no restore command at the the moment

and since #12760 we do store database version within the dump
☝️ this will auto-migrate after dump was restored if nessecary

and with #13108 a check for dump-shema newer than gitea is also handled

[zeripath]

I think now we store the version in the version table that we're safe now. Therefore I think this issue can be closed.