feat(dashboard): implement smart widget collision and category-aware layout

Complete dashboard v2 improvements for better UX and visual consistency:

**1. Push-Aside Drag/Drop (dragDrop.js)**
- Replace swap/revert logic with intelligent reflow algorithm
- When widgets collide on drag, automatically push overlapping widgets down
- All affected widgets repositioned after reflow completes
- Eliminates widget overlap issues

**2. Unified Widget Styling (style.css)**
- Add consistent .rpg-widget container styling for all widgets
- Background: rgba(0,0,0,0.2) for visual separation
- Border-left: 3px highlight for category identification
- Box-shadow and border-radius for depth and polish
- Maintain individual widget decorative styles

**3. Logical Default Layout (defaultLayout.js)**
- Reorganize widgets into semantic clusters with clear comments:
  - USER CLUSTER (top): userInfo → userStats → userMood + userAttributes
  - SCENE CLUSTER (middle): calendar + weather → temp + clock → location
  - SOCIAL CLUSTER (bottom): presentCharacters
- userInfo widget now at top (y=0) as expected
- All positions use rem units for responsive scaling

**4. Category-Aware Auto-Layout (dashboardManager.js)**
- Implement sortWidgetsByCategory() with priority ordering:
  user → scene → social → inventory
- Within user category, specific ordering:
  userInfo → userStats → userMood → userAttributes
- Add preserveOrder option to gridEngine.autoLayout()
- Auto-arrange now uses logical grouping instead of random bin-packing

**5. Multi-Tab Auto-Distribution (dashboardManager.js)**
- Add estimateLayoutHeight() to detect when content exceeds threshold
- Implement distributeWidgetsByCategory() for automatic tab creation:
  - "Status" tab: user + scene widgets
  - "Social" tab: social widgets (if any)
  - "Inventory" tab: inventory widgets (if any)
- Each tab gets category-aware auto-layout
- 80rem height threshold for single-tab limit

**6. Widget Category Metadata (widgets/)**
- Add category field to all widget definitions:
  - userInfo, userStats, userMood, userAttributes: 'user'
  - calendar, weather, temperature, clock, location: 'scene'
  - presentCharacters: 'social'
  - inventory: 'inventory'

**7. Integration Improvements (dashboardIntegration.js)**
- Set default layout on initialization for reset functionality
- Add reset layout button to dashboard header
- Wire up reset button event handler

**8. Core State Management (index.js)**
- Add getInfoBoxData() and setInfoBoxData() to state API
- Ensure info box data persists across sessions

**Technical Details:**
- Rem units throughout for 1080p→4K→mobile responsive scaling
- Reflow algorithm leverages existing gridEngine collision detection
- Category-aware sorting preserves logical relationships
- Multi-tab distribution prevents single-page scroll fatigue
- All changes maintain backwards compatibility with existing layouts

Fixes dashboard issues after rem unit conversion introduced massive positioning bugs.
Users reported widgets overlapping on drag, visual inconsistency, and random auto-arrange behavior.

Related: Epic 2 (Dashboard v2), Phase 3.2

style.css

@@ -1179,6 +1179,13 @@ body:has(.rpg-panel.rpg-position-left) #sheld {
     overflow: hidden;
     display: flex;
     flex-direction: column;
+
+    /* Unified widget styling - consistent look for all widgets */
+    background: rgba(0, 0, 0, 0.2);
+    border-left: 3px solid var(--rpg-highlight);
+    border-radius: 0.5rem;
+    box-shadow: inset 0 0 8px rgba(0, 0, 0, 0.3);
+    padding: 0.5rem;
 }
 
 .rpg-widget > * {