docs(ideai): met à jour les tickets et la mémoire projet après le scaffolding

Ajoute la note mémoire sur l'environnement de dev et reflète l'avancement
du ticket #2 (terminé) et le cadrage du ticket #3 dans les carnets/issues.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.ideai/tickets/index.json

@@ -5,37 +5,37 @@
       "issueRef": "#1",
       "path": "1",
       "title": "[Git] Initialiser le dépôt et la stratégie de branches GameTime",
-      "status": "inProgress",
+      "status": "closed",
       "priority": "high",
       "sprint": null,
       "assignedAgentIds": [
         "8f065f64-ef6e-4a00-af9c-d00be079e3cc"
       ],
-      "updatedAt": 1784301472470
+      "updatedAt": 1784301585782
     },
     {
       "issueRef": "#2",
       "path": "2",
       "title": "[DevBackend] Scaffolding projet Flutter + architecture hexagonale",
-      "status": "open",
+      "status": "closed",
       "priority": "critical",
       "sprint": null,
       "assignedAgentIds": [
         "10ee045b-1c41-479e-ba03-dceed9edd495"
       ],
-      "updatedAt": 1784301371028
+      "updatedAt": 1784304100048
     },
     {
       "issueRef": "#3",
       "path": "3",
       "title": "[DevBackend] Modèle de données Drift complet (entités + migrations)",
-      "status": "open",
+      "status": "inProgress",
       "priority": "critical",
       "sprint": null,
       "assignedAgentIds": [
         "10ee045b-1c41-479e-ba03-dceed9edd495"
       ],
-      "updatedAt": 1784301376032
+      "updatedAt": 1784304100173
     },
     {
       "issueRef": "#4",