## Summary
The messaging/calendar import crons each iterate every active workspace
and execute one `find` per workspace against `core."messageChannel"` /
`core."calendarChannel"` with the shape:
```
WHERE "workspaceId" = $1 AND "isSyncEnabled" = true AND "syncStage" = $2 [AND "type" <> $3]
```
There is currently no index supporting that shape, so the planner does a
seq scan on each table for every iteration. On prod-eu (RDS Performance
Insights, `rds-prod-eu-one`), these two queries are the top two by load
— together ~12 AAS, ~12 calls/sec — and have been the primary
contributor to the sustained 100% CPU since active workspace count grew.
This PR adds composite indexes on `(workspaceId, isSyncEnabled,
syncStage)` for both tables as an instance migration in 2.6.0.
