feat: Replace primsa.$queryRaw() with calls to prisma models

[DafyddLlyr]

What does this PR do?

• Removes all instances of primsa.$queryRaw() and replaces them with calls to the Prisma models
• Remove in-code calculations (e.g. count and average) to aggregate queries
• Renames a few variables to make things a little easier to read

What's not in this PR

• A wider refactor and reorganisation - I've tried to keep this as close as I can to swap of one thing for another. This should keep things more controlled and atomic

Next steps...

It's worth reorganising the code in route.ts to a three-tier architecture with separation of handler (http requests) → service layer (business logic) → data layer (prisma & db).

graph TD
    A[Client] --> B[Handler Layer]
    B[Handler Layer] --> C[Service / Business logic Layer]
    C[Service / Business logic Layer] --> D[Data Access Layer]
    D[Data Access Layer] --> E[Database]

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[DafyddLlyr]

There are a few lines like this, because the db columns are missing a NOT NULL constraint. This is annotated by question marks in the Prisma schema, e.g. Float?

model BuildPrices {
  id                   Int     @id @default(autoincrement())
  houseTypeDescription String? @map("housetypedescription") @db.VarChar(250)
  houseType            String? @map("housetype") @db.VarChar(1)
  priceRange           String? @map("pricerange") @db.VarChar(50)
  priceMid             Float?  @map("pricemid")

  @@map("buildprices")
}

I'll pick this up next - we should be able to update the Prisma schema to generate a migration to do this 🤞

[DafyddLlyr]

I was getting build errors without this - this type guard now narrows postcode down from the union of InvalidPostcode | ValidPostcode to just ValidPostcode

[DafyddLlyr]

Hopefully this is a nice demonstration of the benefits of this approach -

• Type safe queries (no room for typos in raw SQL)
• Safer (relevant XKCD)
• More discoverable code as it's linked by models

[gabrielegranello]

Brilliant, that makes a lot of sense, thanks for explaining

[zz-hh-aa]

Much friendlier code, makes a lot of sense--cheers Daf!