Migrate to FoundryVTT v13 AppV2 +

│ DataModels
│
│ - Reorganize DataModels into src/module/models/ (one .mjs per type)
│ - Create AppV2 actor/item sheets (HandlebarsApplicationMixin)…

src/module/applications/sheets/base-actor-sheet.mjs

@@ -38,7 +38,7 @@ export default class MGT2ActorSheet extends HandlebarsApplicationMixin(foundry.a
         return this._sheetMode === this.constructor.SHEET_MODES.EDIT;
     }
 
-    tabGroups = { primary: "stats" }
+    tabGroups = { sidebar: "health" }
 
     /** @override */
     async _prepareContext() {
@@ -66,6 +66,9 @@ export default class MGT2ActorSheet extends HandlebarsApplicationMixin(foundry.a
     /** @override */
     _onRender(context, options) {
         super._onRender(context, options);
+        // Inject theme class dynamically (can't use game.settings in static DEFAULT_OPTIONS)
+        const theme = game.settings.get("mgt2", "theme");
+        if (theme) this.element.classList.add(theme);
         this._activateTabGroups();
     }