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/item/racialAbility-sheet.hbs

@@ -9,17 +9,25 @@ SPDX-License-Identifier: MIT
     {{> systems/ds4/templates/sheets/item/components/item-header.hbs}}
 
     {{!-- Sheet Tab Navigation --}}
-    <nav class="ds4-sheet-tab-nav tabs" data-group="primary">
-        <a class="ds4-sheet-tab-nav__item" data-action="changeTab" data-tab="description">{{localize 'DS4.HeadingDescription'}}</a>
-        <a class="ds4-sheet-tab-nav__item" data-action="changeTab" data-tab="effects">{{localize 'DS4.HeadingEffects'}}</a>
+    <nav class="tabs" data-group="primary">
+        {{#each tabs}}
+        <a class="item {{cssClass}}" data-tab="{{id}}" data-group="{{group}}">
+            {{#if icon}}<i class="{{icon}}"></i>{{/if}}
+            {{label}}
+        </a>
+        {{/each}}
     </nav>
 
     {{!-- Sheet Body --}}
-    <section class="ds4-sheet-body">
+    <section class="sheet-body">
         {{!-- Description Tab --}}
-        {{> systems/ds4/templates/sheets/item/tabs/description.hbs}}
+        <div class="tab {{#if tabs.description}}{{tabs.description.cssClass}}{{/if}}" data-tab="description" data-group="primary">
+            {{> systems/ds4/templates/sheets/item/tabs/description.hbs}}
+        </div>
 
         {{!-- Effects Tab --}}
-        {{> systems/ds4/templates/sheets/item/tabs/effects.hbs}}
+        <div class="tab {{#if tabs.effects}}{{tabs.effects.cssClass}}{{/if}}" data-tab="effects" data-group="primary">
+            {{> systems/ds4/templates/sheets/item/tabs/effects.hbs}}
+        </div>
     </section>
 </form>