fix(years): format academic years as 2016/17 across all views, remove legacy frontend and data

Apply formatAcademicYear to all year displays in ComparisonChart, ComparisonView,
PerformanceChart, and RankingsView. Remove old vanilla JS frontend and CSV data
directory — both superseded by the Next.js app and Meltano pipeline.

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

nextjs-app/components/RankingsView.tsx

@@ -8,7 +8,7 @@
 import { useRouter, usePathname, useSearchParams } from 'next/navigation';
 import { useComparison } from '@/hooks/useComparison';
 import type { RankingEntry, Filters, MetricDefinition } from '@/lib/types';
-import { formatPercentage, formatProgress, schoolUrl } from '@/lib/utils';
+import { formatPercentage, formatProgress, formatAcademicYear, schoolUrl } from '@/lib/utils';
 import { EmptyState } from './EmptyState';
 import styles from './RankingsView.module.css';
 
@@ -199,11 +199,11 @@ export function RankingsView({
             className={styles.filterSelect}
           >
             <option value="">
-              {filters.years.length > 0 ? `${Math.max(...filters.years)} (Latest)` : 'Latest'}
+              {filters.years.length > 0 ? `${formatAcademicYear(Math.max(...filters.years))} (Latest)` : 'Latest'}
             </option>
             {filters.years.map((year) => (
               <option key={year} value={year}>
-                {year}
+                {formatAcademicYear(year)}
               </option>
             ))}
           </select>