Fixes https://github.com/twentyhq/twenty/issues/18148
## Problem
- Scrolling down in the "no value" kanban column never loads additional
records when it's the only column that needs pagination
- `useTriggerRecordBoardFetchMore` — `.filter(isDefined)` removes `null`
from the list of group values to fetch, and `null` is the value used by
"no value" columns, causing early exit
- `useTriggerRecordBoardFetchMore` — the inline `{ in: [...values] }`
filter cannot express a NULL match, so even without the early exit the
query would be wrong
## Fix
- "No value" column now triggers pagination correctly —
`useTriggerRecordBoardFetchMore` (removed `.filter(isDefined)` so `null`
values pass through)
- Query filter correctly matches NULL field values —
`useTriggerRecordBoardFetchMore` (replaced inline `{ in: [...] }` with
`computeRecordGroupOptionsFilter` which generates `{ is: 'NULL' }` for
null values and `{ in: [...] }` for non-null values)
