Add acknowledge all alerts feature

Add POST /api/alerts/acknowledge-all endpoint to bulk acknowledge all
unacknowledged alerts. Add "Ack All" button to alerts page header with
confirmation dialog for quick dismissal of all pending alerts.

app/web/templates/alerts.html

@@ -6,9 +6,14 @@
 <div class="row mt-4">
     <div class="col-12 d-flex justify-content-between align-items-center mb-4">
         <h1>Alert History</h1>
-        <a href="{{ url_for('main.alert_rules') }}" class="btn btn-primary">
-            <i class="bi bi-gear"></i> Manage Alert Rules
-        </a>
+        <div>
+            <button class="btn btn-success me-2" onclick="acknowledgeAllAlerts()">
+                <i class="bi bi-check-all"></i> Ack All
+            </button>
+            <a href="{{ url_for('main.alert_rules') }}" class="btn btn-primary">
+                <i class="bi bi-gear"></i> Manage Alert Rules
+            </a>
+        </div>
     </div>
 </div>
 
@@ -265,5 +270,34 @@ function acknowledgeAlert(alertId) {
         alert('Failed to acknowledge alert');
     });
 }
+
+function acknowledgeAllAlerts() {
+    if (!confirm('Acknowledge all unacknowledged alerts?')) {
+        return;
+    }
+
+    fetch('/api/alerts/acknowledge-all', {
+        method: 'POST',
+        headers: {
+            'Content-Type': 'application/json',
+            'X-API-Key': localStorage.getItem('api_key') || ''
+        },
+        body: JSON.stringify({
+            acknowledged_by: 'web_user'
+        })
+    })
+    .then(response => response.json())
+    .then(data => {
+        if (data.status === 'success') {
+            location.reload();
+        } else {
+            alert('Failed to acknowledge alerts: ' + (data.message || 'Unknown error'));
+        }
+    })
+    .catch(error => {
+        console.error('Error:', error);
+        alert('Failed to acknowledge alerts');
+    });
+}
 </script>
 {% endblock %}