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

src/systems/dashboard/dashboardTemplate.html

@@ -8,6 +8,11 @@
         </div>
 
         <div class="rpg-dashboard-header-right">
+            <!-- Reset Layout Button -->
+            <button id="rpg-dashboard-reset-layout" class="rpg-dashboard-btn rpg-reset-layout-btn" title="Reset to Default Layout">
+                <i class="fa-solid fa-rotate-left"></i>
+            </button>
+
             <!-- Auto-Layout Button -->
             <button id="rpg-dashboard-auto-layout" class="rpg-dashboard-btn rpg-auto-layout-btn" title="Auto-Arrange Widgets">
                 <i class="fa-solid fa-table-cells-large"></i>