Reorganizes the merchant dashboard into a tab-based layout:
- Tabs: Merchant | Shipping | Stalls | Products | Messages | Orders
- Publish dropdown with NIP-15 options (NIP-99 disabled/coming soon)
- Consistent UI patterns across all tabs:
- Search/filter/buttons aligned right
- Actions column on right side of tables
- Equal-width tabs
- Stalls tab: popup edit dialog, navigation to Products/Orders
- Products tab: filter icon dropdown for stall filtering
- Modular component structure for each tab section
- Fixed product API calls to use correct endpoints
Closes#119🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
