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>

static/style.css

@@ -594,6 +594,10 @@
   color: var(--text-muted);
   font-family: var(--font);
 }
+.topo-legend-item--offrack {
+  border: 1px dashed var(--border-color);
+  padding: 1px 5px;
+}
 .topo-legend-line-10g { width: 24px; height: 2px; background: var(--green); display: inline-block; box-shadow: 0 0 4px rgba(0,255,136,.5); }
 .topo-legend-line-1g  { width: 24px; height: 0; border-top: 2px dashed var(--amber); display: inline-block; }
 .topo-legend-line-wan { width: 24px; height: 2px; background: linear-gradient(to right, var(--cyan), var(--green)); display: inline-block; }