Handle empty asm scratches differently

[ethteck]

We currently allow submitting asm-less (well, empty asm at least) scratches to the site, but we treat them in the UI like they're normal scratches.

https://decomp.me/scratch/p9Q5K

This one, for example, still shows the Target side (but it's empty). The embed also looks confusing

I propose

• a db migration that adds a flag to Scratch which determines if it's one-sided.
  • We can look at existing scratches' asm to make this determination (if the asm is text format and if the text is empty)
• Hiding the target side of the diff window if the Scratch is one-sided
• Changing the embed to remove the "☑ Matched" and instead say "just some cod"* or something
• Consider adjusting the frontend/backend to allow creating scratches with the asm field unset entirely, which makes the scratch one-sided

* probably something better

[ethteck]

Alternative: we don't call these Scratches at all and call them something different entirely, whether that's just a new table in the backend or also reflected in the frontend. My proposal is that we call these Goofs

[ethteck]

or Snips

[mkst]

Itch