Add configurable notification TTL (#24829)

* add configurable ttl for active alert notifications

Notifications sent while an alert was active always used a TTL of 0, so the push service dropped them if the device wasn't reachable at that moment and users only received the notification sent when the alert ended. A new `ttl` notifications option, settable globally or per camera, lets the push service retry these notifications for that many seconds. It defaults to 0, and the settings UI warns that a non-zero value can deliver stale notifications.

* make notification ttl a global advanced setting

- Read `ttl` from the global notifications config and hide it on the camera form
- Show it under Advanced Settings on the Notifications page
- Remove extra padding that misaligned the Notifications cards with the rest of the form
- Shorten the ttl warning

* tweaks

* use enum instead of raw seconds value

web/src/components/config-form/sectionExtras/NotificationsSettingsExtras.tsx

@@ -340,7 +340,7 @@ export default function NotificationsSettingsExtras({
       set(nextNotifications, "enabled", desiredEnabled);
       const sanitizedNotifications = sanitizeSectionData(
         nextNotifications as ConfigSectionData,
-        ["enabled_in_config", "email"],
+        ["enabled_in_config", "email", "ttl"],
       );
       onPendingDataChange("notifications", camera.name, sanitizedNotifications);
       pendingCameraOverridesRef.current.add(camera.name);
@@ -490,7 +490,7 @@ export default function NotificationsSettingsExtras({
 
   return (
     <div className="flex size-full flex-col md:flex-row">
-      <div className="scrollbar-container order-last mb-2 mt-2 flex h-full w-full flex-col overflow-y-auto px-2 md:order-none">
+      <div className="scrollbar-container order-last mb-2 mt-2 flex h-full w-full flex-col overflow-y-auto md:order-none">
         <div className={cn("w-full max-w-5xl space-y-6")}>
           {isAdmin && (
             <SettingsGroupCard