feat: auto-trigger scheduled agents + fix stale nextRun display

- Add background scheduler in entrypoint: calls /api/cron/agents every
  5 minutes to trigger due agents automatically
- Recalculate stale nextRun (past dates) in getAgents() so the display
  always shows a future time
- Agent card shows "En attente de déclenchement" instead of "il y a X"
  when nextRun is in the past

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/app/actions/agent-actions.ts

@@ -206,6 +206,26 @@ export async function getAgents() {
       orderBy: { createdAt: 'desc' }
     })
 
+    // Fix stale nextRun: recalculate if in the past for scheduled agents
+    const now = new Date()
+    for (const agent of agents) {
+      if (agent.frequency !== 'manual' && agent.nextRun && new Date(agent.nextRun) < now) {
+        const nextRun = calculateNextRun({
+          frequency: agent.frequency,
+          scheduledTime: agent.scheduledTime,
+          scheduledDay: agent.scheduledDay,
+          timezone: agent.timezone,
+        })
+        if (nextRun) {
+          await prisma.agent.update({
+            where: { id: agent.id },
+            data: { nextRun },
+          })
+          agent.nextRun = nextRun
+        }
+      }
+    }
+
     return agents
   } catch (error) {
     console.error('Error fetching agents:', error)