fix(dashboard): fix persistent px values, auto-layout, widget loss, gaps, and tabs

This commit resolves 6 critical dashboard issues reported by user:

1. **Persistent px values causing 264rem widget heights**
   - Root cause: state.js had hardcoded rowHeight: 80, gap: 12 (px)
   - Root cause: index.js double-loaded layout, overwriting migration
   - Fix: Changed state.js gridConfig to rem units (5, 0.75)
   - Fix: Removed redundant applyDashboardConfig in index.js
   - Fix: Added migration in layoutPersistence.js for old saves
   - Dashboard now uses rem consistently throughout

2. **Auto-layout on first load**
   - Added auto-layout in loadLayout() when no saved layout exists
   - Prevents overlap from hardcoded default positions
   - Saves auto-laid-out result as initial layout

3. **Reset layout causes overlap**
   - Added auto-layout loop in resetLayout() after applying config
   - Each tab auto-lays out to prevent widget overlap

4. **Auto-arrange loses inventory/social widgets**
   - Fixed autoLayoutWidgets to gather ALL widgets from ALL tabs
   - Previously only gathered current tab, lost other tabs
   - Now always uses multi-tab distribution to preserve all widgets

5. **Auto-arrange leaves 2x2 gaps**
   - Added compact pass in gridEngine.js after bin-packing
   - Moves widgets upward to fill gaps
   - Eliminates empty spaces at bottom of layout

6. **Tabs not compact (icon-only)**
   - Updated tab styling: icons only, names show on hover
   - Allows more tabs in compact space
   - min-width: 2.5rem, larger icon size

Also added debug logging to track config values through initialization.

Fixes refresh sizing bug, reset overlap, widget loss, and layout gaps.

src/core/state.js

@@ -87,8 +87,8 @@ export let extensionSettings = {
             // Columns calculated dynamically by GridEngine (2-4 based on panel width)
             // Mobile (≤1000px screen): always 2 columns
             // Desktop (>1000px screen): 2-4 columns based on panel width
-            rowHeight: 80,         // Pixels per row
-            gap: 12,               // Gap between widgets (px)
+            rowHeight: 5,          // rem units for responsive scaling
+            gap: 0.75,             // rem units (was 12px)
             snapToGrid: true,      // Auto-snap enabled
             showGrid: true         // Show grid lines in edit mode
         },