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/components/TopBar.tsx

@@ -26,6 +26,32 @@ export function TopBar({ onSearchClick }: TopBarProps) {
         zIndex: 100,
       }}
     >
+      {/* Skip to main content link (only visible on focus) */}
+      <a
+        href="#main-content"
+        className="skip-link"
+        style={{
+          position: 'absolute',
+          top: '-40px',
+          left: '0',
+          background: 'var(--accent)',
+          color: '#FFFFFF',
+          padding: '8px 16px',
+          textDecoration: 'none',
+          zIndex: 101,
+          borderRadius: '0 0 4px 0',
+          fontSize: '13px',
+          fontWeight: 600,
+        }}
+        onFocus={(e) => {
+          e.currentTarget.style.top = '0'
+        }}
+        onBlur={(e) => {
+          e.currentTarget.style.top = '-40px'
+        }}
+      >
+        Skip to main content
+      </a>
       {/* Brand */}
       <div className="flex items-center gap-2 shrink-0">
         <Home
@@ -131,7 +157,10 @@ export function TopBar({ onSearchClick }: TopBarProps) {
       </button>
 
       {/* Session info (right) */}
-      <div className="flex items-center gap-2 sm:gap-3 shrink-0">
+      <div
+        className="flex items-center gap-2 sm:gap-3 shrink-0"
+        aria-label="Active session information"
+      >
         <span
           className="hidden sm:inline"
           style={{