Before the item is at Tip, we don't download / upload the store,
this now is shown on screen should the user hit the 'store now'
button to make the UX clearer.
While doing a write-up I realized that an 8 byte hash is still super
overkill to isolate one transaction in a specific wallet while we also
know the block-height it is at.
This limits it to 3 bytes, which should be plenty and thereby shring the
export size quite nicely.