feat: sidebar redimensionnable — drag handle entre sidebar et contenu

- sidebar-resize.tsx: hook useSidebarResize (localStorage persistence, 280-560px)
- sidebar-resize-client.tsx: wrapper layout qui applique la largeur
- layout.tsx: remplace div statique par SidebarResizeClient
- Resize handle: barre 1px→3px au hover, brand-accent pendant drag
- pointer events (pas mouse) pour support tactile
- cursor: col-resize + userSelect:none pendant le drag

L'utilisateur peut maintenant réduire ou élargir la zone de carnet
en glissant la barre entre le sidebar et le contenu principal.

memento-note/app/(main)/layout.tsx

@@ -7,6 +7,7 @@ import { detectUserLanguage, parseAcceptLanguage } from "@/lib/i18n/detect-user-
 import { loadTranslations } from "@/lib/i18n/load-translations";
 import { getAISettings } from "@/app/actions/ai-settings";
 import { AIChatLayoutBridge } from "@/components/ai-chat-layout-bridge";
+import { SidebarResizeClient } from "@/components/sidebar-resize-client";
 
 
 export default async function MainLayout({
@@ -36,8 +37,8 @@ export default async function MainLayout({
       initialAiProcessingConsent={aiSettings?.aiProcessingConsent === true}
     >
       {/* No top-bar header — sidebar-only navigation (architectural-grid design) */}
-      <div className="flex h-screen overflow-hidden bg-memento-desk dark:bg-background">
-        <Suspense fallback={<div className="hidden w-80 md:w-[26rem] 2xl:w-[30rem] shrink-0 md:block h-full self-stretch" />}>
+      <SidebarResizeClient>
+        <Suspense fallback={<div className="hidden w-80 shrink-0 md:block h-full self-stretch" />}>
           <Sidebar user={session?.user} />
         </Suspense>
 
@@ -47,9 +48,9 @@ export default async function MainLayout({
           </a>
           {children}
         </main>
+      </SidebarResizeClient>
 
-        {showAIAssistant && <AIChatLayoutBridge />}
-      </div>
+      {showAIAssistant && <AIChatLayoutBridge />}
     </ProvidersWrapper>
   );
 }