[FEAT] Admin control over user merchant additions

[BenGWeeks]

Problem

Currently, users can freely add merchants to the marketplace view. Some admins may want to curate a controlled list of merchants rather than allowing open additions.

Proposed Solution

Add an admin setting to control merchant discovery behavior:

Configuration Options

Merchant Addition Mode

• open - Users can freely add any merchant by npub/naddr
• curated - Only admin-defined merchants are visible
• hybrid - Default merchants set by admin, users can add more

Admin Features

• Define a list of approved/default merchants
• Option to allow/disallow user additions
• Ability to blocklist specific merchants
• Moderate user-added merchants (approve before visible)

User Experience

• Clear indication of which mode is active
• In curated mode: hide "Add Merchant" functionality
• In hybrid mode: distinguish between official and user-added merchants

Use Cases

• Curated: Local community market with vetted sellers only
• Open: Public discovery marketplace (current behavior)
• Hybrid: Default trusted merchants with option to explore more

Benefits

• Flexibility for different deployment scenarios
• Quality control for curated marketplaces
• Trust signals for users (admin-approved vs user-added)
• Protection against spam or malicious merchants

Related

• Issue [FEAT] Admin customization: themes, titles, and branding #10: Admin customization features
• Issue [FEAT] Default sellers and NIP-65 relay discovery for new users #8