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directory — both superseded by the Next.js app and Meltano pipeline.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/ComparisonChart.tsx

@@ -18,7 +18,7 @@ import {
   ChartOptions,
 } from 'chart.js';
 import type { ComparisonData } from '@/lib/types';
-import { CHART_COLORS } from '@/lib/utils';
+import { CHART_COLORS, formatAcademicYear } from '@/lib/utils';
 
 // Register Chart.js components
 ChartJS.register(
@@ -68,7 +68,7 @@ export function ComparisonChart({ comparisonData, metric, metricLabel }: Compari
   });
 
   const chartData = {
-    labels: years.map(String),
+    labels: years.map(formatAcademicYear),
     datasets,
   };