feat(ui/alerts): SilenceRuleMenu — 1h/8h/24h/custom duration menu

Used by InboxPage row + bulk actions to silence an alert's underlying
rule for a chosen preset window. 'Custom…' routes to
/alerts/silences?ruleId=<id> (T13 adds the prefill wire).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/src/pages/Alerts/SilenceRuleMenu.tsx

@@ -0,0 +1,71 @@
+import { BellOff } from 'lucide-react';
+import { useNavigate } from 'react-router';
+import { Button, Dropdown, useToast } from '@cameleer/design-system';
+import type { DropdownItem } from '@cameleer/design-system';
+import { useCreateSilence } from '../../api/queries/alertSilences';
+
+interface Props {
+  ruleId: string;
+  ruleTitle?: string;
+  onDone?: () => void;
+  variant?: 'row' | 'bulk';
+}
+
+const PRESETS: Array<{ label: string; hours: number }> = [
+  { label: '1 hour',   hours: 1  },
+  { label: '8 hours',  hours: 8  },
+  { label: '24 hours', hours: 24 },
+];
+
+export function SilenceRuleMenu({ ruleId, ruleTitle, onDone, variant = 'row' }: Props) {
+  const navigate = useNavigate();
+  const { toast } = useToast();
+  const createSilence = useCreateSilence();
+
+  const handlePreset = (hours: number) => async () => {
+    const now = new Date();
+    const reason = ruleTitle
+      ? `Silenced from inbox (${ruleTitle})`
+      : 'Silenced from inbox';
+    try {
+      await createSilence.mutateAsync({
+        matcher: { ruleId },
+        reason,
+        startsAt: now.toISOString(),
+        endsAt: new Date(now.getTime() + hours * 3_600_000).toISOString(),
+      });
+      toast({ title: `Silenced for ${hours}h`, variant: 'success' });
+      onDone?.();
+    } catch (e) {
+      toast({ title: 'Silence failed', description: String(e), variant: 'error' });
+    }
+  };
+
+  const handleCustom = () => {
+    navigate(`/alerts/silences?ruleId=${encodeURIComponent(ruleId)}`);
+  };
+
+  const items: DropdownItem[] = [
+    ...PRESETS.map(({ label, hours }) => ({
+      label,
+      disabled: createSilence.isPending,
+      onClick: handlePreset(hours),
+    })),
+    { divider: true, label: '' },
+    { label: 'Custom…', onClick: handleCustom },
+  ];
+
+  const buttonLabel = variant === 'bulk' ? 'Silence rules' : 'Silence rule…';
+
+  return (
+    <Dropdown
+      trigger={
+        <Button variant="secondary" size="sm">
+          <BellOff size={14} style={{ marginRight: 4 }} />
+          {buttonLabel}
+        </Button>
+      }
+      items={items}
+    />
+  );
+}