feat(notifications): add preview deploy/rebuild alert choices

[orkasi]

Summary

Adds two optional notification switches for preview lifecycle events:

• Preview Deploy: first preview deployment for a PR
• Preview Rebuild: subsequent preview rebuilds triggered by new commits

Problem

Preview jobs currently do not have dedicated notification controls, so teams cannot subscribe differently to first deploys vs follow-up rebuilds.

What changed

• Added previewDeploy and previewRebuild notification fields (DB schema + migration).
• Exposed both fields in notification create/update schemas and service persistence paths.
• Added both toggles to Notification Settings UI and wired load/reset/submit for all providers.
• Tagged preview webhook jobs as:
  • previewDeploy for first PR preview
  • previewRebuild when the preview already exists and a new commit arrives
• Passed that event through queue/API payloads.
• Updated preview deployment/rebuild flows to send:
  • success notifications using the correct preview event toggle
  • build-error notifications on preview failures (existing build-error channel)

Validation

• pnpm --filter @dokploy/server typecheck
• pnpm --filter dokploy typecheck
• pnpm --filter dokploy test -- __test__/deploy/github.test.ts