feat: CECE identity persistence to SQLite

[blackboxprogramming]

Summary

CECE's identity (cece-profile.json) should persist to SQLite with full relationship/skill/experience tracking.

Acceptance Criteria

• Import cece-profile.json into cece-identity.db on startup
• GET /cece/identity returns current state
• Relationships updated on agent interactions
• Export endpoint GET /cece/export → JSON

Labels: area:agents, type:feature, priority:p1