docs: all features free, pay only to remove marketplace fee

Commit notes

Final model - maximum generosity:

FREE (everything included): - 100GB storage - All AI features (tagging, descriptions) - Full analytics - Unlimited workspaces/projects - Sell unlimited packs - 15% marketplace fee on sales only

PRO (€9/mo): - Same features - 0% marketplace fee - Priority support

LABEL (€29/mo): - 500GB storage - Team members - Multiple artist profiles

Philosophy: No artificial scarcity. No feature gates. The fee is the monetization. Subscription removes it. User upgrades when their own math says it's worth it.

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