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/components/AdminShell.js

@@ -1,10 +1,10 @@
 'use client';
 
-import AdminSidebar from './AdminSidebar';
 import { useState } from 'react';
-import AdminHeader from './AdminHeader';
+import AdminSidebar from './AdminSidebar.js';
+import AdminHeader from './AdminHeader.js';
 
-export default function AdminPagesLayout({ children, user, onLogout, appName, enabledModules, navigationSections }) {
+export default function AdminShell({ children, user, onLogout, appName, navigationSections }) {
   const [isMobileMenuOpen, setIsMobileMenuOpen] = useState(false);
 
   return (
@@ -13,11 +13,17 @@ export default function AdminPagesLayout({ children, user, onLogout, appName, en
         isMobileMenuOpen={isMobileMenuOpen}
         setIsMobileMenuOpen={setIsMobileMenuOpen}
         appName={appName}
-        enabledModules={enabledModules}
         navigationSections={navigationSections}
       />
       <div className="flex-1 flex flex-col min-w-0">
-        <AdminHeader isMobileMenuOpen={isMobileMenuOpen} setIsMobileMenuOpen={setIsMobileMenuOpen} user={user} onLogout={onLogout} appName={appName} navigationSections={navigationSections} />
+        <AdminHeader
+          isMobileMenuOpen={isMobileMenuOpen}
+          setIsMobileMenuOpen={setIsMobileMenuOpen}
+          user={user}
+          onLogout={onLogout}
+          appName={appName}
+          navigationSections={navigationSections}
+        />
         <main className="flex-1 overflow-y-auto bg-neutral-50 dark:bg-black">
           <div className="px-8 py-7 pb-32 max-w-[1920px] mx-auto">
             {children}

src/features/admin/components/index.js

@@ -1,6 +1,6 @@
-/**
- * Admin Components Exports
- */
+'use client';
 
-export { default as AdminPagesClient } from './AdminPages.js';
-export { default as AdminPagesLayout } from './AdminPagesLayout.js';
+export { default as AdminShell } from './AdminShell.js';
+export { default as AdminSidebar } from './AdminSidebar.js';
+export { default as AdminHeader } from './AdminHeader.js';
+export { default as ThemeToggle } from './ThemeToggle.js';