fix: tag badges and buttons using bg-accent with unreadable text

bg-accent (#f97316 orange) with text-muted-foreground (#848b9b gray)
is nearly invisible. Replaced with bg-elevated + border pattern for
readable contrast across TagBadges, StepForm, StepDetailModal, and
StepLibraryBrowser. Also fixed emerald → success-dim token.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/step-library/StepLibraryBrowser.tsx

@@ -226,7 +226,7 @@ export function StepLibraryBrowser({ onInsert, onCreateNew, showCreateButton = f
                     'rounded-full px-2.5 py-1 text-xs transition-colors',
                     selectedTag === tag.tag
                       ? 'bg-primary text-white'
-                      : 'bg-accent text-muted-foreground hover:bg-accent'
+                      : 'border border-border bg-[var(--color-bg-elevated)] text-muted-foreground hover:text-foreground hover:border-[var(--color-border-hover)]'
                   )}
                 >
                   {tag.tag} ({tag.count})