feat(insights): bouton Fit view sur le graphe — reset zoom + clear focus

- zoomRef stocke le behavior d3.zoom pour accès externe au useEffect
- handleFitView: d3.zoomIdentity reset (600ms transition) + clear selectedClusterId
- Bouton Maximize2 en haut à droite du graphe avec aria-label
- cursor-pointer + focus-visible:ring pour a11y

memento-note/components/network-graph.tsx

@@ -2,6 +2,7 @@
 
 import { useEffect, useRef } from 'react'
 import * as d3 from 'd3'
+import { Maximize2 } from 'lucide-react'
 
 interface Note {
   id: string
@@ -49,6 +50,7 @@ export function NetworkGraph({
 }: NetworkGraphProps) {
   const svgRef = useRef<SVGSVGElement>(null)
   const containerRef = useRef<HTMLDivElement>(null)
+  const zoomRef = useRef<any>(null)
 
   useEffect(() => {
     if (!svgRef.current || !containerRef.current) return
@@ -67,6 +69,7 @@ export function NetworkGraph({
         g.attr('transform', event.transform)
       })
 
+    zoomRef.current = zoom
     svg.call(zoom as any)
 
     // Filter notes with cluster assignments
@@ -348,6 +351,15 @@ export function NetworkGraph({
     }
   }, [notes, clusters, bridgeNotes, onNoteSelect, selectedClusterId])
 
+  const handleFitView = () => {
+    if (!svgRef.current || !zoomRef.current) return
+    d3.select(svgRef.current)
+      .transition()
+      .duration(600)
+      .call(zoomRef.current.transform, d3.zoomIdentity)
+    onClusterSelect?.(null)
+  }
+
   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 */}
@@ -378,6 +390,15 @@ export function NetworkGraph({
           </button>
         )}
       </div>
+      {/* Fit view button */}
+      <button
+        onClick={handleFitView}
+        className="absolute top-6 right-6 z-10 flex items-center gap-1.5 px-3 py-1.5 rounded-full border border-border/40 bg-white/90 dark:bg-black/80 text-concrete hover:text-ink dark:hover:text-dark-ink hover:border-concrete/40 text-[9px] font-bold uppercase tracking-wider transition-all shadow-sm cursor-pointer focus-visible:ring-2 focus-visible:ring-ochre/50 focus-visible:outline-none backdrop-blur-sm"
+        aria-label={fitViewLabel}
+      >
+        <Maximize2 size={11} />
+        {fitViewLabel}
+      </button>
       <svg ref={svgRef} className="w-full h-full" />
     </div>
   )