feat: add group quota summary

[MiaoZang]

Summary

• add an OpenAI group quota summary endpoint and route
• show 5H / 7D usage buckets in the admin group table
• include all account statuses when repository support is available, so disabled/error accounts with snapshots are included in the summary
• include small Windows compile fixes needed for local Go test runs on Windows

Tests

• go test ./internal/service ./internal/handler/admin ./internal/repository -run 'TestAdminService_GetGroupQuotaSummary|TestGroupHandler|TestAccountRepoSuite/TestListByGroup' -count=1 -p 1
• pnpm exec vitest run src/components/admin/group/tests/GroupQuotaSummaryModal.spec.ts src/views/admin/tests/GroupsView.spec.ts
• git diff --cached --check