[Phase 4] Implement Brand Kit Management System

[VenkataAnilKumar]

Goal

Implement Brand Kit management so each workspace can persist and reuse logos, fonts, colors, and tone settings during generation.

Scope

• Brand setup wizard in web app
• Upload/store brand assets in R2 via presigned URLs
• Persist brand profile in Postgres scoped by workspace
• Validate logo/font file types and size limits

Acceptance Criteria

• Workspace admin can create/update brand kit
• Brand kit values are available to brief and generation pipeline
• Invalid files are rejected with clear error messages