refactor: extract _annotate_suppressions helper, remove orphaned CSS

- Extract identical suppression-annotation loop from index() and
  api_status() into _annotate_suppressions() helper to eliminate DRY
  violation
- Improve stuck-job error message: 'thread crash' → 'no activity for
  5 minutes' (less alarming, more accurate)
- Remove orphaned .events-filter-bar CSS class (never referenced in
  any template or JS file)

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

static/style.css

@@ -214,8 +214,6 @@
   padding: 1px 7px;
 }
 .g-section-actions  { margin-left: auto; }
-.events-filter-bar  { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
-.events-filter-bar .lt-input-sm { width: 220px; }
 .sev-pills          { display: flex; gap: 4px; }
 .g-page-sub { font-size: .78em; color: var(--text-muted); margin-top: 4px; }
 .g-page-sub-aside { font-size: .78em; color: var(--text-muted); margin-left: 8px; }