feat: implement clean Foundry V13 compliant tab system

- Remove custom tab implementation in favor of official ApplicationV2 tabs
- Implement ApplicationTab typedef structure for Actor and Item sheets
- Add memory-safe event listener management with proper cleanup
- Update all sheet templates to use standard Foundry tab structure
- Add template safety checks to prevent undefined access errors
- Optimize performance with DOM updates instead of full re-renders
- Maintain backward CSS compatibility during transition
- Add dynamic tab configuration based on item types

Key improvements:
- ~200 lines of custom tab code removed
- Memory leak prevention with proper event cleanup
- Performance optimization (no re-render on tab switch)
- Standards-compliant with Foundry V13 ApplicationV2 API
- Consistent implementation across Actor and Item sheets
- Template safety with Handlebars guards
- Dynamic icon and localization support

All 31 modified files now use the official Foundry VTT v13 tab system.

templates/sheets/actor/tabs/spells.hbs

@@ -42,7 +42,7 @@ titleKey=titleKey}}
 
 {{!-- ======================================================================== --}}
 
-<div class="ds4-sheet-tab tab spells" data-group="primary" data-tab="spells">
+
     {{#unless (isEmpty itemsByType.spell)}}
     <ol class="ds4-embedded-document-list ds4-embedded-document-list--spell item-list">
         {{#> systems/ds4/templates/sheets/actor/components/item-list-header.hbs isEquipable=true hideDescription=true
@@ -79,6 +79,7 @@ titleKey=titleKey}}
             '')}}{{item.system.spellModifier.numerical}}{{else}}{{item.system.spellModifier.complex}}{{/if}}
         </div>
 
+
         {{!-- max. distance --}}
         {{> distanceUnit titleKey='DS4.SpellDistance' unitDatum=item.system.maxDistance
         config=@root/config}}
@@ -96,4 +97,3 @@ titleKey=titleKey}}
     {{/unless}}
     {{> systems/ds4/templates/sheets/shared/components/add-button.hbs title='DS4.UserInteractionAddItemTitle'
     documentType='item' type='spell'}}
-</div>