refactor(ui): move 'Enable Immersive HTML' toggle to settings panel

Moved the 'Enable Immersive HTML' toggle from main panel to settings:
- Added toggle to settings.html with descriptive notes
- Removed from template.html to free vertical space
- Checkbox ID remains the same so existing JS still works

Benefits:
- Frees up vertical space in dashboard (was causing scrollbars)
- Users can now use full 3x7 grid instead of being limited to 3x6
- Eliminates gap beneath last widget
- Toggle is still accessible but doesn't clutter main panel
- Settings panel is the appropriate place for infrequently-changed options

template.html

@@ -54,15 +54,6 @@
                 </div>
             </div>
 
-            <!-- HTML Prompt Toggle -->
-            <div class="rpg-toggle-container">
-                <label class="rpg-toggle-label">
-                    <input type="checkbox" id="rpg-toggle-html-prompt">
-                    <i class="fa-solid fa-code"></i>
-                    <span>Enable Immersive HTML</span>
-                </label>
-            </div>
-
             <!-- Manual Update Button -->
             <button id="rpg-manual-update" class="rpg-btn-primary rpg-manual-update-btn">
                 <i class="fa-solid fa-sync"></i> Refresh RPG Info