Task 20: Accessibility audit improvements

Semantic HTML:
- Changed Card component from div to article element
- Added id="main-content" to main element for skip link target

Keyboard Navigation & ARIA:
- Added skip link to TopBar (visible only on focus, navigates to #main-content)
- Added aria-label="Active session information" to session info container
- Added aria-hidden="true" to all decorative colored dots (CardHeader, CareerActivity, Projects, Sidebar status badge)
- All expandable items already have role="button", tabIndex={0}, aria-expanded
- All KPI cards already have proper aria-label describing flip state
- Command palette already has full ARIA implementation (combobox, listbox, dialog)

Focus Management:
- Added global focus-visible styles in index.css (2px accent outline, 2px offset)
- Buttons, links, inputs all have proper focus rings with accent color
- Command palette focus trap already implemented

Reduced Motion:
- All components already check prefers-reduced-motion at module scope
- Dashboard entrance, tile expansion, KPI flip, palette animations respect reduced motion
- Added reduced motion override for pulse animation (disables pulse, keeps static dot)

Color Contrast:
- All color tokens already meet WCAG AA standards per ref spec
- Tertiary text (#8DA8A5) used only for supplementary labels where information is conveyed elsewhere

Quality checks: typecheck ✓, lint ✓ (1 pre-existing warning), build ✓

src/index.css

@@ -371,3 +371,39 @@ html {
     to { transform: none; opacity: 1; }
   }
 }
+
+/* ===== FOCUS VISIBLE STYLES (WCAG Compliance) ===== */
+/* Default focus ring for all focusable elements */
+*:focus-visible {
+  outline: 2px solid rgba(13, 110, 110, 0.4);
+  outline-offset: 2px;
+}
+
+/* Button-like interactive elements */
+button:focus-visible,
+[role="button"]:focus-visible,
+[role="option"]:focus-visible {
+  outline: 2px solid rgba(13, 110, 110, 0.4);
+  outline-offset: 2px;
+}
+
+/* Links */
+a:focus-visible {
+  outline: 2px solid rgba(13, 110, 110, 0.4);
+  outline-offset: 2px;
+}
+
+/* Inputs and textareas */
+input:focus-visible,
+textarea:focus-visible {
+  outline: 2px solid rgba(13, 110, 110, 0.6);
+  outline-offset: 0px;
+}
+
+@media (prefers-reduced-motion: reduce) {
+  /* Disable pulse animation on status badge dot */
+  @keyframes pulse {
+    0%, 100% { opacity: 1; }
+    50% { opacity: 1; }
+  }
+}