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/locales/ja.json

@@ -2920,5 +2920,88 @@
     "copyRefFailed": "Could not copy block reference",
     "copyRefNoNote": "Save the note before copying a block reference",
     "copyRefUnsupported": "This block type cannot be referenced yet"
+  },
+  "insightsView": {
+    "title": "セマンティックインサイト",
+    "subtitle": "知識の隠された構造を発見",
+    "resync": "ネットワークを再同期",
+    "mapping": "マッピング中…",
+    "loading": "ノート読み込み中…",
+    "mappingTitle": "知識をマッピング中…",
+    "mappingHint": "This can take one to three minutes. You can keep browsing; the page will update when it's done.",
+    "analyzeNow": "セマンティック分析を開始",
+    "emptyNeedMoreNotes": "Add {count} more notes to unlock semantic clustering (minimum 10).",
+    "embeddingsHint": "AI索引付き：{indexed}/{total}ノートのみ。",
+    "vsGraphHint": "This is not the same as “Link map” (network icon in the sidebar): here, AI groups your notes by theme.",
+    "openGraphMap": "リンクマップを開く",
+    "analysisFailed": "分析失敗。AI設定を確認。",
+    "analysisSuccess": "分析完了：{count}テーマ検出。",
+    "analysisNoClusters": "テーマ未検出。",
+    "staleResults": "前回分析の結果を表示。",
+    "semanticGraphLegend": "テーマ概覧（リンクマップではない）",
+    "fitGraphView": "全体表示",
+    "graphPreviewHint": "Theme overview: the number is how many notes belong here. Hover a dot for the title, click to open. Full list on the right.",
+    "graphMoreNotes": "+{count} more in this theme",
+    "graphNotesLabel": "ノート",
+    "clusterFallback": "テーマ {index}",
+    "unclusteredNotes": "{count} notes not assigned to a theme (hidden from graph).",
+    "emptyTitle": "知識クラスターを発見",
+    "emptyDescription": "Click \"Re-sync network\" to analyze your notes and find hidden connections",
+    "stats": {
+      "clusters": "クラスター",
+      "bridgeNotes": "ブリッジノート"
+    },
+    "clusters": {
+      "title": "Semantic clusters",
+      "notesCount": "{count} notes",
+      "centralNotes": "Central notes",
+      "emptyCluster": "No notes in this cluster"
+    },
+    "bridgeNotes": {
+      "title": "Powerful bridge notes",
+      "score": "スコア：{score}%",
+      "empty": "No significant bridge notes yet. Deepen your research to find new connections."
+    },
+    "suggestions": {
+      "title": "Missing links (AI generated)",
+      "bridging": "{clusterA}と{clusterB}を接続",
+      "emptyTitle": "提案なし",
+      "emptyDescription": "All your clusters may already be connected!",
+      "createNote": "ブリッジノート作成"
+    },
+    "unknownNote": "無題",
+    "viewSplit": "Split",
+    "viewGraph": "グラフ",
+    "viewDashboard": "ダッシュボード",
+    "isolatedClusters": {
+      "title": "Isolated clusters ({count})",
+      "badge": "未接続",
+      "empty": "全クラスター接続済み！"
+    },
+    "focusCluster": {
+      "title": "クラスターフォーカス中",
+      "description": "This thematic cluster gathers {count} complementary notes. Click on a note to access it directly:",
+      "close": "閉じる"
+    },
+    "badgeDominant": "Dominant",
+    "bridgeCount": "ブリッジ",
+    "echoTitle": "You keep returning to this idea",
+    "tipClusters": "AI grouped your notes by semantic affinity — regardless of which notebook they're in. Each theme represents a subject your mind keeps returning to.",
+    "tipClustersAction": "Click a theme to see its notes. Click a note to open it.",
+    "tipBridgeNotes": "These notes speak to two different themes at once. They reveal where your thinking crosses boundaries — often where the most original ideas hide.",
+    "tipBridgeNotesAction": "Click a note to open it and understand the connection.",
+    "tipEcho": "Memory Echo detects two notes written at very different times that cover the same idea. Your mind revisited a thought without realising it.",
+    "tipEchoAction": "Two notes, same idea, different moments. Click to explore.",
+    "tipSuggestions": "These themes have no note linking them yet. AI proposes a starting idea. Click 'Create bridge note' to write it and open it in the editor.",
+    "tipSuggestionsAction": "Click 'Create bridge note' to write the note and open it immediately.",
+    "tipIsolated": "These themes are isolated: no note connects them to the others. Maybe you're exploring a fragile idea? One synthesis note would be enough to create the link.",
+    "tipIsolatedAction": "These themes have no note connecting them to the rest of your thinking.",
+    "recalcSystem": {
+      "title": "再計算システム",
+      "statusSynced": "同期済み",
+      "scheduledCron": "予定済み",
+      "lastSync": "前回同期"
+    },
+    "resetFocus": "フォーカス解除"
   }
 }