docs: simplify to one free tier with 15% marketplace fee

Commit notes

Key changes: - Remove arbitrary limits (no pack limits, no "become a creator" gate) - Everyone can sell on free tier, pay 15% only when they earn - User decides when to upgrade based on their own math - Show savings calculation in dashboard, let them decide

Model: - Free: €0, 15% marketplace fee, 10GB storage - Pro: €9/mo, 0% fee, 100GB storage - Label: €29/mo, 0% fee, 500GB, team features

Breakeven: €60/month in sales makes Pro worth it Dashboard shows: "You sold €X, on Pro you'd keep €Y more"

No manipulation, just transparency. User decides when the math works.

Co-authored-by: armin.naimi <[email redacted]>