Add collapsible panel, fix inventory scrolling, adjust toggle margins

- Add collapse/expand toggle button to side panels (left/right positions)
- Button shows on the outside edge of the panel with chevron icon
- Panel collapses to 40px vertical bar, button icon direction updates based on position
- Fix inventory box stretching issue by adding max/min height constraints
- Inventory items now scroll internally with flex layout
- Remove bottom margin from Enable Immersive HTML toggle
- Add top margin to Manual Update button to maintain spacing

template.html

@@ -1,4 +1,9 @@
 <div id="rpg-companion-panel" class="rpg-panel">
+    <!-- Collapse/Expand Toggle Button -->
+    <button class="rpg-collapse-toggle" id="rpg-collapse-toggle" title="Collapse/Expand Panel">
+        <i class="fa-solid fa-chevron-right"></i>
+    </button>
+
     <!-- Main Game Panel -->
     <div class="rpg-game-container">
         <!-- Header with Controls -->