feat(web): live SSE log tail and log retention setting

web/app/settings/page.tsx

@@ -168,6 +168,9 @@ export default function SettingsPage() {
   const [toAddrs, setToAddrs] = useState(""); // comma-separated in UI
   const [useTLS, setUseTLS] = useState(false);
 
+  // Workflow log retention (days). 0 = keep forever.
+  const [logRetentionDays, setLogRetentionDays] = useState(30);
+
   const [saved, setSaved] = useState(false);
 
   useEffect(() => {
@@ -183,11 +186,15 @@ export default function SettingsPage() {
     setFromAddr(settings.email?.from_addr ?? "");
     setToAddrs((settings.email?.to_addrs ?? []).join(", "));
     setUseTLS(settings.email?.use_tls ?? false);
+    setLogRetentionDays(settings.workflow_log_retention_days ?? 30);
   }, [settings]);
 
   const { mutate: save, isPending } = useMutation({
-    mutationFn: (payload: { alerts: AlertSettings; email: EmailSettings }) =>
-      api.saveSettings(payload),
+    mutationFn: (payload: {
+      alerts: AlertSettings;
+      email: EmailSettings;
+      workflow_log_retention_days?: number | null;
+    }) => api.saveSettings(payload),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ["settings"] });
       setSaved(true);
@@ -218,6 +225,7 @@ export default function SettingsPage() {
         to_addrs: toList,
         use_tls: useTLS,
       },
+      workflow_log_retention_days: logRetentionDays,
     });
   }
 
@@ -374,6 +382,29 @@ export default function SettingsPage() {
           </div>
         </Card>
 
+        {/* Workflow logs */}
+        <Card>
+          <CardHeader>
+            <CardTitle>Workflow Logs</CardTitle>
+          </CardHeader>
+          <p className="mb-5 text-sm text-text-secondary">
+            How long to keep workflow run logs on the server before they are
+            automatically deleted.
+          </p>
+          <Field
+            label="Log retention (days)"
+            hint="0 = keep forever. Applies to per-run step output logs."
+          >
+            <input
+              type="number"
+              min={0}
+              value={logRetentionDays}
+              onChange={(e) => setLogRetentionDays(Number(e.target.value))}
+              className="w-32 rounded-lg border border-border bg-surface-2 px-3 py-2 text-sm text-text-primary focus:border-accent/50 focus:outline-none focus:ring-1 focus:ring-accent/30"
+            />
+          </Field>
+        </Card>
+
         <div className="flex items-center gap-3">
           <Button type="submit" variant="primary" loading={isPending}>
             {saved ? "Saved!" : "Save Settings"}