feat(insights): UX gap closure — i18n, network graph, recalc panel, toasts

Bugs fixes:
- network-graph.tsx: 2 strings hardcoded FR → props i18n (untitledLabel, resetFocusLabel)
- Panneau recalcul: clés i18n réutilisées avec mauvais sens → nouvelles clés recalcSystem.*
- 13 locales: section insightsView.* complète (67 clés × 13 = 871 traductions)

UX features:
- Hint /insights ≠ /graph (semanticGraphLegend + lien vers /graph)
- Toasts succès/échec/zéro-clusters après analyse (analysisSuccess/Failed/NoClusters)
- État vide différencié: emptyNeedMoreNotes si < 10 notes
- Tips contextuels sections Bridge Notes et Suggestions

Sprint:
- 4 epics marqués done (3,4,5,6 — toutes stories terminées)
- sprint-status.yaml last_updated corrigé

memento-note/components/network-graph.tsx

@@ -31,6 +31,9 @@ interface NetworkGraphProps {
   onNoteSelect: (id: string) => void
   selectedClusterId?: string | null
   onClusterSelect?: (id: string | null) => void
+  untitledLabel?: string
+  resetFocusLabel?: string
+  fitViewLabel?: string
 }
 
 export function NetworkGraph({
@@ -39,7 +42,10 @@ export function NetworkGraph({
   bridgeNotes,
   onNoteSelect,
   selectedClusterId = null,
-  onClusterSelect
+  onClusterSelect,
+  untitledLabel = 'Untitled',
+  resetFocusLabel = 'Reset focus',
+  fitViewLabel = 'Fit view',
 }: NetworkGraphProps) {
   const svgRef = useRef<SVGSVGElement>(null)
   const containerRef = useRef<HTMLDivElement>(null)
@@ -268,7 +274,7 @@ export function NetworkGraph({
       .attr('fill', '#4b5563')
       .attr('class', 'dark:fill-zinc-300 font-sans pointer-events-none')
       .text(d => {
-        const title = d.title || 'Sans titre'
+        const title = d.title || untitledLabel
         return title.length > 20 ? title.substring(0, 18) + '...' : title
       })
 
@@ -368,7 +374,7 @@ export function NetworkGraph({
             onClick={() => onClusterSelect?.(null)}
             className="px-3 py-1.5 rounded-full border border-rose-200 bg-rose-50 dark:bg-rose-950/20 dark:border-rose-900/40 text-rose-500 text-[9px] font-bold uppercase tracking-wider hover:bg-rose-100 dark:hover:bg-rose-950/30 transition-all shadow-sm"
           >
-            Réinitialiser focus
+            {resetFocusLabel}
           </button>
         )}
       </div>