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/links.html

@@ -6,7 +6,7 @@
 <div class="lt-page-header">
   <div>
     <h1 class="lt-page-title">Link Debug</h1>
-    <p class="g-page-sub" style="margin-top:4px">
+    <p class="g-page-sub">
       Per-interface stats: speed, duplex, SFP optical levels, TX/RX rates, errors, and carrier changes.
       <span id="links-updated" style="margin-left:8px"></span>
     </p>