feat(api): add v2 lookup endpoints

[wklken]

Summary

• add /api/v2/open/gateways/-/lookup/ with ids and names filters
• add /api/v2/open/mcp-servers/permissions/apply-records/-/lookup/ with an ids filter
• add /api/v2/sync/gateways/{gateway_name}/resource_versions/-/lookup/ with ids and versions filters
• preserve the existing list APIs and register each lookup API with the same gateway resource configuration as its list API
• add API docs and focused regression coverage

Verification

• uv run make edition-ee && uv run make lint-check
  • ruff, mypy, import-linter passed
  • API consistency: 0 errors; 41 existing warnings
• uv run make test
  • 3831 passed
• git diff --cached --check
• parsed gateway resource comparison: all three lookup configs match their corresponding list configs except backend path