fix(insights): sidebar user-controlled + cluster chips organisées

Sidebar (UX: User Freedom):
- Visible par défaut sur /insights (pas caché par le système)
- Toggle via bouton hamburger: toggle-insights-sidebar event
- Préférence persistée en localStorage (insights-sidebar-collapsed)
- User décide: voir ou cacher le sidebar

Cluster chips:
- Triées par taille (plus grand cluster en premier)
- Compteur de notes par cluster (badge arrondi)
- max-w-[120px] sur le nom pour éviter overflow
- padding/gap plus compacts (px-2.5 py-1 gap-1.5)

memento-note/components/network-graph.tsx

@@ -362,22 +362,27 @@ export function NetworkGraph({
 
   return (
     <div ref={containerRef} className="w-full h-full bg-paper dark:bg-[#121212] rounded-3xl overflow-hidden border border-border/40 relative">
-      {/* Pastilles de cluster — cliquables pour activer le focus */}
-      <div className="absolute top-6 left-6 z-10 flex flex-wrap gap-2 max-w-[90%]">
-        {clusters.map(c => {
+      {/* Pastilles de cluster — triées par taille, avec compteurs */}
+      <div className="absolute top-6 left-6 z-10 flex flex-wrap gap-1.5 max-w-[85%]">
+        {[...clusters]
+          .sort((a, b) => b.noteIds.length - a.noteIds.length)
+          .map(c => {
           const isSelected = String(c.id) === selectedClusterId
           return (
             <button
               key={c.id}
               onClick={() => onClusterSelect?.(isSelected ? null : String(c.id))}
-              className={`flex items-center gap-1.5 px-3 py-1.5 rounded-full border shadow-sm transition-all text-[9px] font-bold uppercase tracking-wider ${
+              className={`flex items-center gap-1.5 px-2.5 py-1 rounded-full border transition-all text-[9px] font-bold uppercase tracking-wider cursor-pointer focus-visible:ring-2 focus-visible:ring-ochre/50 focus-visible:outline-none ${
                 isSelected
                   ? 'bg-ink text-white dark:bg-white dark:text-black border-ink dark:border-white scale-105 shadow-md'
-                  : 'bg-white/90 dark:bg-black/80 text-concrete hover:text-ink hover:border-concrete/40 border-border'
+                  : 'bg-white/90 dark:bg-black/80 text-concrete hover:text-ink hover:border-concrete/40 border-border shadow-sm'
               }`}
             >
-              <div className="w-1.5 h-1.5 rounded-full" style={{ backgroundColor: c.color }} />
-              <span>{c.name ?? String(c.id)}</span>
+              <div className="w-2 h-2 rounded-full shrink-0" style={{ backgroundColor: c.color }} />
+              <span className="truncate max-w-[120px]">{c.name ?? String(c.id)}</span>
+              <span className={`text-[8px] px-1 rounded-full shrink-0 ${isSelected ? 'bg-white/20' : 'bg-black/5 dark:bg-white/10'}`}>
+                {c.noteIds.length}
+              </span>
             </button>
           )
         })}