Task 18: Add command palette (Ctrl+K)

- Create CommandPalette.tsx with overlay, search input, grouped results,
  keyboard navigation (arrows, Enter, Escape), and footer hints
- Rebuild search.ts with PaletteItem model: 24 entries across 6 sections
  (Experience, Core Skills, Active Projects, Achievements, Education,
  Quick Actions) matching concept HTML structure
- Fuzzy search via fuse.js with weighted keys (title, subtitle, keywords)
- Wire into DashboardLayout with global Ctrl+K listener and TopBar click
- Action system: scroll-to-tile, expand-item, external links, download CV
- Add data-tile-id to all Card/tile components for scroll targeting
- CSS animations: palette-overlay-in, palette-modal-in with
  prefers-reduced-motion support
- Maintain backward-compatible legacy exports for ClinicalSidebar
  (will be removed in Task 21)

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

src/index.css

@@ -337,3 +337,25 @@ html {
     grid-template-columns: 1fr;
   }
 }
+
+/* ===== COMMAND PALETTE ANIMATIONS ===== */
+@keyframes palette-overlay-in {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
+@keyframes palette-modal-in {
+  from { transform: scale(0.97) translateY(-8px); opacity: 0; }
+  to { transform: scale(1) translateY(0); opacity: 1; }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  @keyframes palette-overlay-in {
+    from { opacity: 1; }
+    to { opacity: 1; }
+  }
+  @keyframes palette-modal-in {
+    from { transform: none; opacity: 1; }
+    to { transform: none; opacity: 1; }
+  }
+}