Task 13: Build CareerActivity tile

Created CareerActivityTile component with full timeline merged from multiple data sources:
- Builds 10 activity entries matching the concept HTML spec exactly
- Color-coded dots by type: role (teal), project (amber), cert (green), edu (purple)
- Two-column responsive grid (1 column below 900px)
- Entry types: 4 roles, 2 projects, 3 certifications, 1 education
- Data sources: consultations, investigations, documents
- Sorted newest-first with stable ordering for same-year entries
- Added .activity-grid responsive CSS class to index.css
- Wired into DashboardLayout below LastConsultationTile

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/components/DashboardLayout.tsx

@@ -6,6 +6,7 @@ import { PatientSummaryTile } from './tiles/PatientSummaryTile'
 import { LatestResultsTile } from './tiles/LatestResultsTile'
 import { CoreSkillsTile } from './tiles/CoreSkillsTile'
 import { LastConsultationTile } from './tiles/LastConsultationTile'
+import { CareerActivityTile } from './tiles/CareerActivityTile'
 
 const prefersReducedMotion = window.matchMedia('(prefers-reduced-motion: reduce)').matches
 
@@ -109,6 +110,8 @@ export function DashboardLayout() {
             <LastConsultationTile />
 
             {/* CareerActivityTile — full width */}
+            <CareerActivityTile />
+
             {/* EducationTile — full width */}
             {/* ProjectsTile — full width */}
           </div>