feat(sdlc): staging environment + automated staging→prod pipeline

- pr-checks.yml: PR gate — frontend typecheck+jest, backend import smoke,
  image builds (no push), Claude AI review posted as PR comment (severe
  findings block merge)
- deploy.yml (replaces build-and-push.yml): merge to main builds+pushes
  images tagged sha-<sha>/staging, deploys the staging Portainer stack via
  webhook, runs Playwright E2E journeys against staging, then retags the
  verified images :prod (previous kept as :prod-previous) and deploys prod
- docker-compose.portainer.staging.yml: second Portainer stack — :staging
  images, sc_staging_* names, own macvlan IPs, Airflow on 8081; data
  bootstrapped from source via the staging Airflow DAGs
- prod compose now pins :prod instead of :latest (only the promotion step
  moves it; :latest is no longer published)
- e2e/: 6 Playwright journeys (search, postcode, detail, compare, rankings)
  driven by BASE_URL — the promotion gate
- scripts/ci/ai_review.py: Claude review with structured JSON findings
- docs/DEPLOY.md: full SDLC doc incl. one-time setup checklist and rollback
- replaced removed 'next lint' with tsc typecheck; fixed stale jest tests
  (slug URLs, N/A formatting, stable trend, fake-timer setup)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PqGhF93UrpDNvXBLMjJENL

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

@@ -19,7 +19,7 @@ describe('formatPercentage', () => {
   });
 
   it('handles null values', () => {
-    expect(formatPercentage(null)).toBe('-');
+    expect(formatPercentage(null)).toBe('N/A');
   });
 });
 
@@ -31,7 +31,7 @@ describe('formatProgress', () => {
   });
 
   it('handles null values', () => {
-    expect(formatProgress(null)).toBe('-');
+    expect(formatProgress(null)).toBe('N/A');
   });
 });
 
@@ -44,16 +44,16 @@ describe('calculateTrend', () => {
     expect(calculateTrend(70, 75)).toBe('down');
   });
 
-  it('calculates same trend', () => {
-    expect(calculateTrend(75, 75)).toBe('same');
+  it('calculates stable trend', () => {
+    expect(calculateTrend(75, 75)).toBe('stable');
   });
 
   it('handles null previous value', () => {
-    expect(calculateTrend(75, null)).toBe('same');
+    expect(calculateTrend(75, null)).toBe('stable');
   });
 
   it('handles null current value', () => {
-    expect(calculateTrend(null, 75)).toBe('same');
+    expect(calculateTrend(null, 75)).toBe('stable');
   });
 });
 
@@ -72,7 +72,13 @@ describe('isValidPostcode', () => {
 });
 
 describe('debounce', () => {
-  jest.useFakeTimers();
+  beforeEach(() => {
+    jest.useFakeTimers();
+  });
+
+  afterEach(() => {
+    jest.useRealTimers();
+  });
 
   it('delays function execution', () => {
     const mockFn = jest.fn();
@@ -100,8 +106,6 @@ describe('debounce', () => {
     expect(mockFn).toHaveBeenCalledWith('third');
     expect(mockFn).toHaveBeenCalledTimes(1);
   });
-
-  jest.useRealTimers();
 });
 
 describe('buildOfstedListBadge', () => {