Use plain strings for map zones

[tsa96]

Refactors backend/DB so that zones are stored as plain text rather than jsonb.

With incoming map cache changes, we perform a hash check on map load to check zone files match the hash on the zoneHash field of the MapVersion table. Currently, zones are stored in Postgres as jsonb, a Postgres-specific binary serialization of JSON. It doesn't store whitespace, so makes storing zone hashes unreliable - it's probably possible to get the hash check to be consistent but I was struggling to get it working and felt very messy.

The main purpose of jsonb is to allow queries over that JSON data, which for zones we never need to do - we're really just using using the field for storage. The only thing we gain from using jsonb is that Prisma queries automatically parse the JSON into JSOs for us; this change requires we stick some JSON.parses in the backend code, but it's really not a big deal.

I haven't spent the time benching/profiling anything, but I suspect this method is quite a lot more performant overall, since the maps/<mapID>/zones GETs can just return raw strings, rather than having to serialize and deserialize each time, and that endpoint is called very frequently by the game.

Checks

• !! DONT IGNORE ME !! I have ran nx run db:create-migration <name> and committed the migration if I've made DB schema changes
• I have included/updated tests where applicable (see Testing)
• I have followed semantic commit messages e.g. feat: Add foo, chore: Update bar, etc...
• My branch has a clear history of changes that can be easy to follow when being reviewed commit-by-commit
• My branch is functionally complete; the only changes to be done will be those potentially requested in code review
• All changes requested in review have been fixuped into my original commits