perf: batch N+1 per-row Supabase queries into single .in() calls

[chiptus]

Problem

Four call sites fire one Supabase request per array item inside Promise.all(items.map(async ...)) instead of a single batched query:

• src/api/groups/useUserGroups.ts:44-59 (addMemberCounts) — one count query per group.
• src/api/groups/useGroupMembers.ts:25-41 — one profiles query per member.
• src/api/admin-roles/useAdminRolesQuery.ts:23-36 — one profiles query per admin role.
• src/pages/admin/Analytics/AnalyticsTable.tsx:45-57 and :71-83 — one count query per group and per user.

Fix

Replace with a single .in("id", ids) (or .in("group_id", ids) + client-side grouping via Map) call at each site. Same shape of fix everywhere; real latency win as groups/admins/users grow. Can be combined with the AnalyticsTable.tsx → src/api/ refactor ticket since it touches the same file.