fix(groups): resolve internal user before listing

[rissrice2105-agent]

Summary

• resolve the authenticated Supabase user to the app's internal users.id
• pass that internal UUID to get_user_groups
• return 404 without calling the RPC when the internal profile is missing

Bug

get_user_groups filters group_members.user_id, which references users.id, but the route passed auth.users.id. Those UUIDs differ, so authenticated users could receive an empty group list.

Tests

• pnpm exec vitest run src/app/api/chat/groups/route.test.js
• pnpm exec eslint src/app/api/chat/groups/route.js src/app/api/chat/groups/route.test.js
• pnpm test:ci (81 files, 482 tests)

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