Safety mesh — youth tier defaults

Youth-tier programs (Youth League, Travel Club, sometimes School Athletics) ship with safety defaults that don't apply to college / pro.

Defaults:
1. **Coach SafeSport certification** — every coach must hold an active SafeSport cert (verified via the platform Vendor Compliance Registry). Coaches without active certs cannot be assigned to a youth team roster.
2. **Film moderation** — every film clip uploaded on the org side flows through the platform image-moderation pipeline (`onImageUploaded` → `moderationStatus`). Clips pending review aren't visible to athletes / parents until reviewed.
3. **Coach↔minor messaging audit** — any direct message between a coach and a minor on the platform is audit-logged via the Safety Mesh signal bus. The log is reviewable by program admins and (with parental consent) parents.
4. **Parent / guardian gate** — for athletes under 13, all athlete-facing UI is parent-mediated. The parent's account is linked to the minor's via the Guardian module; parents control consent for film visibility, talent-network opt-in, recruiting contact, etc.

Pro tier turns these off by default (different legal regime). Switching tier mid-season requires admin approval and triggers a re-audit.