Phase 3 foundation: entities, relationships, ownership, source-of-truth, and
snapshot rules for the structured career profile. Relational children
(Experience/Education/Skill/Project/Certification/Language) under CareerProfile;
long tail as JSON; blob (ProfileCvStructureJson) becomes a derived projection for
legacy read paths; lazy non-destructive backfill.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>