Complete Next.js migration with SSR and Docker deployment

- Migrate from vanilla JavaScript SPA to Next.js 16 with App Router
- Add server-side rendering for all pages (Home, Compare, Rankings)
- Create individual school pages with dynamic routing (/school/[urn])
- Implement Chart.js and Leaflet map integrations
- Add comprehensive SEO with sitemap, robots.txt, and JSON-LD
- Set up Docker multi-service architecture (PostgreSQL, FastAPI, Next.js)
- Update CI/CD pipeline to build both backend and frontend images
- Fix Dockerfile to include devDependencies for TypeScript compilation
- Add Jest testing configuration
- Implement performance optimizations (code splitting, caching)

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

nextjs-app/__tests__/lib/utils.test.ts

@@ -0,0 +1,104 @@
+/**
+ * Utility Functions Tests
+ */
+
+import {
+  formatPercentage,
+  formatProgress,
+  calculateTrend,
+  isValidPostcode,
+  debounce,
+} from '@/lib/utils';
+
+describe('formatPercentage', () => {
+  it('formats percentages correctly', () => {
+    expect(formatPercentage(75.5)).toBe('75.5%');
+    expect(formatPercentage(100)).toBe('100.0%');
+    expect(formatPercentage(0)).toBe('0.0%');
+  });
+
+  it('handles null values', () => {
+    expect(formatPercentage(null)).toBe('-');
+  });
+});
+
+describe('formatProgress', () => {
+  it('formats progress scores correctly', () => {
+    expect(formatProgress(2.5)).toBe('+2.5');
+    expect(formatProgress(-1.3)).toBe('-1.3');
+    expect(formatProgress(0)).toBe('0.0');
+  });
+
+  it('handles null values', () => {
+    expect(formatProgress(null)).toBe('-');
+  });
+});
+
+describe('calculateTrend', () => {
+  it('calculates upward trend', () => {
+    expect(calculateTrend(75, 70)).toBe('up');
+  });
+
+  it('calculates downward trend', () => {
+    expect(calculateTrend(70, 75)).toBe('down');
+  });
+
+  it('calculates same trend', () => {
+    expect(calculateTrend(75, 75)).toBe('same');
+  });
+
+  it('handles null previous value', () => {
+    expect(calculateTrend(75, null)).toBe('same');
+  });
+
+  it('handles null current value', () => {
+    expect(calculateTrend(null, 75)).toBe('same');
+  });
+});
+
+describe('isValidPostcode', () => {
+  it('validates correct UK postcodes', () => {
+    expect(isValidPostcode('SW1A 1AA')).toBe(true);
+    expect(isValidPostcode('M1 1AE')).toBe(true);
+    expect(isValidPostcode('B33 8TH')).toBe(true);
+  });
+
+  it('rejects invalid postcodes', () => {
+    expect(isValidPostcode('INVALID')).toBe(false);
+    expect(isValidPostcode('12345')).toBe(false);
+    expect(isValidPostcode('')).toBe(false);
+  });
+});
+
+describe('debounce', () => {
+  jest.useFakeTimers();
+
+  it('delays function execution', () => {
+    const mockFn = jest.fn();
+    const debouncedFn = debounce(mockFn, 300);
+
+    debouncedFn('test');
+    expect(mockFn).not.toHaveBeenCalled();
+
+    jest.advanceTimersByTime(300);
+    expect(mockFn).toHaveBeenCalledWith('test');
+    expect(mockFn).toHaveBeenCalledTimes(1);
+  });
+
+  it('cancels previous calls', () => {
+    const mockFn = jest.fn();
+    const debouncedFn = debounce(mockFn, 300);
+
+    debouncedFn('first');
+    jest.advanceTimersByTime(150);
+    debouncedFn('second');
+    jest.advanceTimersByTime(150);
+    debouncedFn('third');
+    jest.advanceTimersByTime(300);
+
+    expect(mockFn).toHaveBeenCalledWith('third');
+    expect(mockFn).toHaveBeenCalledTimes(1);
+  });
+
+  jest.useRealTimers();
+});