## Summary
Fixes "missing FROM-clause entry for table" SQL error when using
`orderByForRecords` with a relation field (e.g. `{ company: { name:
"AscNullsFirst" } }`) in a `groupBy` query.
### Root cause
This is a regression from #18005 (Feb 17). That PR correctly removed a
duplicate `applyOrderToBuilder()` call on the groupBy subquery (which
was conflicting with the `ROW_NUMBER() OVER (... ORDER BY ...)` window
function), but in doing so it also removed the LEFT JOINs that
`applyOrderToBuilder` was adding for relation fields.
After that change, ordering relied solely on `getOrderByRawSQL()` inside
`applyPartitionByToBuilder()`, which builds raw SQL for the window
function but never added the required JOINs. Scalar field ordering (e.g.
`name`, `position`) kept working since those don't need JOINs, but
relation field ordering (e.g. `company.name`) broke.
### Fix
- `getOrderByRawSQL` now returns `relationJoins` alongside the SQL
string so callers get the join info they need
- `applyPartitionByToBuilder` in `GroupByWithRecordsService` adds the
required LEFT JOINs before building the `ROW_NUMBER()` window function,
mirroring the pattern used by `applyOrderToBuilder` in the `findMany`
path
## Test plan
- [x] Manually tested locally with a GraphQL query matching the
customer's failing pattern (`orderByForRecords: [{ company: { name:
"AscNullsFirst" } }]`)
- [x] Added integration tests for ascending and descending relation
field ordering in `group-by-with-records-resolver.integration-spec.ts`
- [x] Typecheck passes
- [x] Lint passes
- [x] CI green
