fix(quotas): unifier le décompte IA (BYOK, rollback) et combler les fuites

Centralise la réserve via ai-quota, corrige admin unavailable (-1), brancher les routes sans quota et le host-pays brainstorm, avec usage-meter élargi, noms de clusters, MCP et ajustements dashboard/insights.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/app/api/cron/sync-usage/route.ts

@@ -77,12 +77,12 @@ export async function POST(req: NextRequest) {
           redis.get(`${key}:tokens`),
         ]);
 
-        const periodStart = new Date(`${period}-01`);
-        const periodEnd = new Date(
-          periodStart.getFullYear(),
-          periodStart.getMonth() + 1,
+        const periodStart = new Date(`${period}-01T00:00:00.000Z`);
+        const periodEnd = new Date(Date.UTC(
+          periodStart.getUTCFullYear(),
+          periodStart.getUTCMonth() + 1,
           1,
-        );
+        ));
 
         await prisma.usageLog.upsert({
           where: {