Cleanup: strip redundant inline styles, add CSS classes

- Remove style="margin-top:4px" from .g-page-sub in all three secondary
  pages (the value is already defined in .g-page-sub rule in style.css)
- suppressions.html: replace inline style="padding:12px 14px" with TDS
  lt-section-body class
- index.html topology legend: replace inline dashed-border style with
  .topo-legend-item--offrack modifier class in style.css

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/suppressions.html

@@ -6,7 +6,7 @@
 <div class="lt-page-header">
   <div>
     <h1 class="lt-page-title">Alert Suppressions</h1>
-    <p class="g-page-sub" style="margin-top:4px">Manage maintenance windows and per-target alert suppression rules.</p>
+    <p class="g-page-sub">Manage maintenance windows and per-target alert suppression rules.</p>
   </div>
 </div>
 
@@ -188,7 +188,7 @@
     <span class="lt-frame-bl">&#x255A;</span>
     <span class="lt-frame-br">&#x255D;</span>
     <div class="lt-section-header">Host &amp; Interface Reference</div>
-    <div style="padding:12px 14px">
+    <div class="lt-section-body">
       <div class="targets-grid">
         {% for name, host in snapshot.hosts.items() %}
         <div class="target-card">