Uppercase UID before inserting into DB

After pulling this change in, could you run the following SQL to sanitise the data?

```
create table invalid_cards as select * from cards where uid != upper(uid);
delete from cards where uid in (select uid from invalid_cards);
select count(*) from cards where uid != upper(uid); -- should be 0
```

(lowercase cards won't be working atm anyway, so nobody's losing out here)