feat(alerts): per-group acknowledge button for related alert groups

Adds an 'Ack all (N)' button next to the '+N related' toggle on grouped
alerts. Acknowledges the primary and all related alerts in one action
using the existing bulkAcknowledge API endpoint, without touching
unrelated alerts.

frontend-modern/src/features/alerts/AlertOverviewActiveAlertsSection.tsx

@@ -128,15 +128,31 @@ export function AlertOverviewActiveAlertsSection(props: AlertOverviewActiveAlert
                 />
                 <Show when={group.related.length > 0}>
                   <div class="ml-4 border-l-2 border-border pl-3 mt-1">
-                    <button
-                      type="button"
-                      class="text-xs text-muted hover:text-base-content transition-colors py-1"
-                      onClick={() => toggleGroup(group.key)}
-                    >
-                      {isGroupExpanded(group.key)
-                        ? 'Hide'
-                        : `+${group.related.length} related`}
-                    </button>
+                    <div class="flex items-center gap-3 py-1">
+                      <button
+                        type="button"
+                        class="text-xs text-muted hover:text-base-content transition-colors"
+                        onClick={() => toggleGroup(group.key)}
+                      >
+                        {isGroupExpanded(group.key)
+                          ? 'Hide'
+                          : `+${group.related.length} related`}
+                      </button>
+                      <Show when={[group.primary, ...group.related].some((a) => !a.acknowledged)}>
+                        <button
+                          type="button"
+                          class="text-xs text-blue-600 dark:text-blue-400 hover:text-blue-700 dark:hover:text-blue-300 transition-colors"
+                          onClick={() => {
+                            void props.state.handleGroupAcknowledge([
+                              group.primary,
+                              ...group.related,
+                            ]);
+                          }}
+                        >
+                          Ack all ({group.related.length + 1})
+                        </button>
+                      </Show>
+                    </div>
                     <Show when={isGroupExpanded(group.key)}>
                       <div class="space-y-2 mt-1">
                         <For each={group.related}>

frontend-modern/src/features/alerts/useAlertAcknowledgementState.ts

@@ -184,6 +184,41 @@ export function useAlertAcknowledgementState(props: UseAlertAcknowledgementState
     }
   };
 
+  const handleGroupAcknowledge = async (alerts: Alert[]) => {
+    const pending = alerts.filter((alert) => {
+      const id = getCanonicalAlertId(alert);
+      return !effectiveAlerts().find((e) => getCanonicalAlertId(e) === id)?.acknowledged;
+    });
+    if (pending.length === 0) return;
+
+    const identifiers = pending.map((alert) => getCanonicalAlertId(alert));
+    const groupProcessing = new Set(identifiers);
+    setProcessingAlerts((previous) => new Set([...previous, ...groupProcessing]));
+
+    try {
+      const result = await AlertsAPI.bulkAcknowledge(identifiers);
+      const acknowledgedAt = new Date().toISOString();
+      const successes = result.results.filter((entry) => entry.success);
+
+      successes.forEach((entry) => {
+        applyAlertUpdate(entry.alertIdentifier, {
+          acknowledged: true,
+          ackTime: acknowledgedAt,
+          ackUser: undefined,
+        });
+      });
+
+      if (successes.length > 0) {
+        notificationStore.success(getAlertOverviewBulkAcknowledgedNotification(successes.length));
+      }
+    } catch (error) {
+      logger.error('Group acknowledge failed', error);
+      notificationStore.error(getAlertOverviewBulkAcknowledgeGenericFailureNotification());
+    } finally {
+      groupProcessing.forEach((id) => releaseAlertProcessing(id));
+    }
+  };
+
   return {
     effectiveAlerts,
     unacknowledgedAlerts,
@@ -191,5 +226,6 @@ export function useAlertAcknowledgementState(props: UseAlertAcknowledgementState
     bulkAckProcessing,
     handleAlertAcknowledgement,
     handleBulkAcknowledge,
+    handleGroupAcknowledge,
   };
 }

frontend-modern/src/features/alerts/useAlertOverviewState.ts

@@ -38,6 +38,7 @@ export function useAlertOverviewState(props: UseAlertOverviewStateProps) {
     bulkAckProcessing,
     handleAlertAcknowledgement,
     handleBulkAcknowledge,
+    handleGroupAcknowledge,
   } = useAlertAcknowledgementState({
     alerts: activeAlerts,
     updateAlert: props.updateAlert,
@@ -109,6 +110,7 @@ export function useAlertOverviewState(props: UseAlertOverviewStateProps) {
     bulkAckProcessing,
     handleAlertAcknowledgement,
     handleBulkAcknowledge,
+    handleGroupAcknowledge,
   };
 }