feat(webhooks): pause and resume outbound targets

[phucnguyen1707]

Summary

• let domain owners pause and resume outbound webhook targets without deleting their URL or signing secret
• persist the active state through the owner-scoped API and show active/paused status in the dashboard
• verify paused targets are excluded from delivery selection and cannot be changed through another domain

Tests

• bun test tests/domain-webhook-active.test.mjs (2 passed)
• 136 tests passed across the non-DNS suites plus DNS policy/wire suites; the two existing DNS socket suites hang under Bun 1.3.14 on Windows and are untouched
• npx tsc --noEmit
• npm run build
• git diff --check