feat: objective & Success metrics required when board type is goal

[Qquanwei]

Task / context

• Mission Control task:
• Why: onboarding field is required

Scope

• <bullet 1>
• <bullet 2>

Out of scope

Evidence / validation

• make check (or explain what you ran instead)
• E2E (if applicable): <cypress run / screenshots>
• Logs/links:

Screenshots (UI changes)

Desktop	Mobile

Docs impact

• No user/operator docs changes required
• Docs updated: <paths/links>

Risk / rollout notes

• Risk level: low / medium / high
• Rollback plan (if needed):

Checklist

• Branch created from origin/master (no unrelated commits)
• PR is focused (one theme)
• No secrets in code/logs/docs
• If API/behavior changes: docs updated (OpenAPI + docs/reference/api.md)