feat(ui): site-wide UX/UI audit — unified buttons, tokens, accessibility

- Add shared button system (.btn-primary/secondary/tertiary/active) in globals.css
- Replace 40+ hardcoded rgba() values with design tokens across all CSS modules
- Add skip link, :focus-visible indicators, and ARIA landmarks
- Standardise button labels ("+ Compare" / "✓ Comparing") across all components
- Add collapse/minimize toggle to ComparisonToast
- Fix heading hierarchy (h3→h2 in ComparisonView)
- Add aria-live on search results, aria-label on trend SVGs
- Add "Search" nav link, fix footer empty section, unify max-widths
- Darken --text-muted for WCAG AA compliance (4.6:1 contrast ratio)
- Net reduction of ~180 lines through button style deduplication

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

nextjs-app/components/HomeView.module.css

@@ -47,8 +47,8 @@
   align-items: center;
   gap: 0.5rem;
   padding: 0.5rem 1rem;
-  background: rgba(45, 125, 125, 0.1);
-  border: 1px solid rgba(45, 125, 125, 0.3);
+  background: var(--accent-teal-bg);
+  border: 1px solid rgba(45, 125, 125, 0.25);
   border-radius: 8px;
   font-size: 0.875rem;
   color: var(--accent-teal, #2d7d7d);
@@ -234,52 +234,6 @@
   flex-shrink: 0;
 }
 
-.compactBtn {
-  padding: 0.25rem 0.5rem;
-  font-size: 0.6875rem;
-  font-weight: 600;
-  background: var(--accent-coral, #e07256);
-  color: white;
-  border: none;
-  border-radius: 4px;
-  cursor: pointer;
-  transition: all 0.2s ease;
-  text-align: center;
-}
-
-.compactBtn:hover {
-  background: var(--accent-coral-dark, #c45a3f);
-}
-
-.compactBtn.compactBtnActive {
-  background: var(--bg-secondary, #f3ede4);
-  color: var(--text-secondary, #5c564d);
-  border: 1px solid var(--border-color, #e5dfd5);
-}
-
-.compactBtn.compactBtnActive:hover {
-  background: var(--border-color, #e5dfd5);
-  color: var(--text-primary, #1a1612);
-}
-
-.compactBtnSecondary {
-  padding: 0.25rem 0.5rem;
-  font-size: 0.6875rem;
-  font-weight: 500;
-  background: transparent;
-  color: var(--text-secondary, #5c564d);
-  border: 1px solid var(--border-color, #e5dfd5);
-  border-radius: 4px;
-  cursor: pointer;
-  transition: all 0.2s ease;
-  text-decoration: none;
-  text-align: center;
-}
-
-.compactBtnSecondary:hover {
-  background: var(--bg-secondary, #f3ede4);
-  color: var(--text-primary, #1a1612);
-}
 
 .sectionHeader {
   margin-bottom: 1rem;