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/character-abilities.hbs

@@ -5,7 +5,7 @@ SPDX-FileCopyrightText: 2021 Gesina Schwalbe
 SPDX-License-Identifier: MIT
 --}}
 
-<div class="ds4-sheet-tab tab abilities" data-group="primary" data-tab="abilities">
+
     {{!-- TALENT --}}
     <h4 class="ds4-embedded-document-list-title">{{localize 'DS4.ItemTypeTalentPlural'}}</h4>
     {{#unless (isEmpty itemsByType.talent)}}
@@ -64,4 +64,3 @@ SPDX-License-Identifier: MIT
     {{/unless}}
     {{> systems/ds4/templates/sheets/shared/components/add-button.hbs title='DS4.UserInteractionAddItemTitle'
     documentType='item' type='alphabet'}}
-</div>