feat(dashboard): split user

Stats widget into 4 modular widgets

- Create userInfoWidget (avatar, name, level)
- Refactor userStatsWidget (stats bars only with smart sizing)
- Create userMoodWidget (mood emoji, conditions)
- Create userAttributesWidget (STR/DEX/CON/INT/WIS/CHA)
- Add category field to widgets for auto-layout grouping
- Register all new modular widgets in dashboardIntegration.js

All widgets include getOptimalSize() for smart content-aware auto-layout.
Part of Phase 1 & 3.1 of dashboard modularization plan.

src/systems/dashboard/widgets/inventoryWidget.js

@@ -62,6 +62,7 @@ export function registerInventoryWidget(registry, dependencies) {
         name: 'Inventory',
         icon: '🎒',
         description: 'Full inventory system with On Person, Stored, and Assets',
+        category: 'inventory',
         minSize: { w: 2, h: 4 },
         defaultSize: { w: 2, h: 6 },
         requiresSchema: false,