feat(core)!: introduce runtime extension registry and flat module conventions

BREAKING CHANGE: sup config now derives entries from package.json#exports and a server/client glob instead of manual lists; module structure follows flat + barrel convention with .server.js/.client.js runtime suffixes

src/features/admin/pages/DashboardPage.client.js

@@ -1,33 +1,20 @@
 'use client';
 
-import { getClientWidgets } from '../../dashboard/clientRegistry.js';
-import '../../dashboard/widgets/index.client.js';
-import '../../../dashboard.client.js';
-
-// Évalué après tous les imports : les auto-registrations sont complètes
-const sortedWidgets = getClientWidgets();
+import { getWidgets } from '../registry.js';
 
 export default function DashboardPage({ stats }) {
   const loading = stats === null || stats === undefined;
+  const widgets = getWidgets();
 
   return (
     <div className="flex flex-col gap-4 sm:gap-6 lg:gap-8">
-      <div className="flex items-center justify-between">
-        <div>
-          <h1 className="text-lg sm:text-xl font-semibold text-neutral-900 dark:text-white">
-            Tableau de bord
-          </h1>
-          <p className="mt-1 text-[13px] text-neutral-500 dark:text-neutral-400">Vue d'ensemble de votre application</p>
-        </div>
+      <div>
+        <h1 className="text-lg sm:text-xl font-semibold text-neutral-900 dark:text-white">Tableau de bord</h1>
+        <p className="mt-1 text-[13px] text-neutral-500 dark:text-neutral-400">Vue d'ensemble de votre application</p>
       </div>
-
       <div className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 2xl:grid-cols-4 gap-4 sm:gap-6">
-        {sortedWidgets.map(({ id, Component }) => (
-          <Component
-            key={id}
-            data={loading ? null : (stats[id] ?? null)}
-            loading={loading}
-          />
+        {widgets.map(({ id, Component }) => (
+          <Component key={id} data={loading ? null : (stats[id] ?? null)} loading={loading} />
         ))}
       </div>
     </div>