fix: total count inflated by role JOINs in user and group membership list queries

[oniani1]

Describe the bug

PR #5850 fixed an incorrect total count in the project identity membership list endpoint -- the count was summing role assignments instead of unique identities because of a window function running over JOINed membership_roles rows.

The same bug exists in two sibling files that weren't covered by that fix:

• membership-user-dal.ts (findUsers, line ~228)
• membership-group-dal.ts (findGroups, line ~214)

Both use the same pattern:

.select(
  db.raw(
    `count(${TableName.Membership}."actorUserId") OVER(PARTITION BY ${TableName.Membership}."scopeOrgId") as total`
  )
)

The query JOINs membership_roles (one-to-many), so a user with 3 roles produces 3 rows. The window function counts all rows in the partition, returning 8 instead of 5 for an org with 5 users.

identity-org-dal.ts (searchIdentities, line ~432) has the same issue.

To reproduce

Given 5 users in an org, where 2 users have multiple roles:

User	Roles
alice	admin, developer, reviewer
bob	member, developer
charlie	member
diana	member
eve	viewer

Buggy query result: total_count = 8 (3+2+1+1+1)
Expected result: total_count = 5

Tested on PostgreSQL 14 with the same table structure.

Expected behavior

Total count should reflect the number of unique users/groups/identities, not the number of role assignments.

Fix

The same approach from #5850 works here -- replace the window function with a subquery count over the distinct membership set:

const countQuery = await (tx || db.replicaNode())
  .count("* as total")
  .from(paginatedUsers.clone().as("distinctMemberships"));

Happy to open a PR for this if it makes sense to fix all three in one go.

[linear]

ENG-4772