perf(organizations): eliminate N+1 queries in listMembers and adminDelete

[diogeneszilli]

Summary

• listMembers: Replace per-member enrichUserWithItsProfile() and attributeToUser.findMany() calls with batch operations, reducing from 2N queries to 2 queries
• adminDelete: Replace N individual prisma.user.update() calls with a single batch $executeRaw UPDATE, and convert include to select to fetch only needed fields (id, username, name, slug)

Test plan

• Verify listMembers returns the same response shape with batched enrichment
• Verify adminDelete correctly renames all users in one batch UPDATE
• Verify attribute expansion still works when expand includes "attributes"
• Run yarn type-check:ci --force to confirm no type regressions

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