fix(dashboard): send double-nested pagination in OrgDomains' list query

[lakhansamani]

Summary

• web/dashboard/src/components/OrgDomains.tsx's fetchDomains() sent pagination: { limit: 100 }, but ListOrgDomainsRequest.pagination is PaginatedRequest, which itself wraps a pagination: PaginationRequest field (internal/graph/schema.graphqls) — the correct shape is double-nested: pagination: { pagination: { limit: 100 } } }
• The wrong shape meant every _org_domains query failed server-side with GRAPHQL_VALIDATION_FAILED — silently swallowed (res.data?._org_domains?.org_domains || [] never checked res.error), so the verified-domains table always rendered "No verified domains yet." even when domains existed
• This feature (added in feat(dashboard): add verified org domains UI #707) has never worked since it shipped — every org admin managing verified domains through the dashboard UI would see an empty list regardless of what was actually configured
• Also adds the missing res.error handling fetchDomains lacked, matching the exact pattern already used by every other mutation handler in this file (RequestOrgDomain/VerifyOrgDomain/AddVerifiedOrgDomain/DeleteOrgDomain)
• Added a regression test asserting the exact query variable shape sent — the existing test file's mock client had no schema awareness, which is why this went unnoticed by the pre-existing unit tests for as long as the feature existed

Found while building an e2e spec that drives this UI through a real browser and backend (not the mocked client the existing unit tests use).

Test plan

• npx vitest run src/components/OrgDomains.test.tsx — 6/6 pass (5 pre-existing + 1 new regression test asserting the correct double-nested shape)
• Full npx vitest run (web/dashboard) — 43/43 pass, no regressions
• npm run build clean

[lakhansamani]

Superseded by #723 (pagination schema standardization), which was built directly on top of this fix and includes it inline — both PRs touched the exact same lines in OrgDomains.tsx/OrgDomains.test.tsx. #723 has now merged, so this branch's diff is fully redundant (and now conflicts, since main already contains equivalent content in a different shape). Closing rather than force-resolving conflicts for a no-op.