UI consistency (page shell 2/N): automations adopts .page-shell card

First of the "flat -> card" conversions. The automations list view sat
directly on the page background (.automations-container = bare padding) while
its inner .dashboard-header is the same header dashboard uses. Adopt
.page-shell so the page becomes a floating gradient card structurally
identical to the dashboard (page-shell card > dashboard-header > content).

- Drop .automations-container's bespoke `padding: 20px 24px` (card padding now
  from .page-shell); keep the class as the mobile/JS hook.
- Add `page-shell` to the container in markup.

Visible change by design (this page was not previously a card). Mobile keeps
its existing .automations-container padding override.

webui/index.html

@@ -2280,7 +2280,7 @@
             <div class="page" id="automations-page">
                 <!-- List View -->
                 <div class="automations-list-view" id="automations-list-view">
-                    <div class="automations-container">
+                    <div class="page-shell automations-container">
                         <div class="dashboard-header">
                             <div class="header-text">
                                 <h2 class="header-title"><img src="/static/automation.png" class="page-header-icon" alt=""><span>Automations</span></h2>

webui/static/style.css

@@ -43838,7 +43838,7 @@ body.downloads-disabled [onclick*="DownloadMissing"]:not([onclick*="close"]) {
    AUTOMATIONS PAGE
    =========================== */
 
-.automations-container { padding: 20px 24px; }
+/* .automations-container: card styling from .page-shell */
 .automations-list { display: flex; flex-direction: column; gap: 0; }
 #automations-list-view { padding-bottom: 10vh; }