feat: implement v0.4.0 - Reports, Charts, Comparison, Dark Mode, E2E Testing

Backend (@backend-dev):
- Add ReportService with PDF/CSV generation (reportlab, pandas)
- Implement Report API endpoints (POST, GET, DELETE, download)
- Add ReportRepository and schemas
- Configure storage with auto-cleanup (30 days)
- Rate limiting: 10 downloads/minute
- Professional PDF templates with charts support

Frontend (@frontend-dev):
- Integrate Recharts for data visualization
- Add CostBreakdown, TimeSeries, ComparisonBar charts
- Implement scenario comparison page with multi-select
- Add dark/light mode toggle with ThemeProvider
- Create Reports page with generation form and list
- Add new UI components: checkbox, dialog, tabs, label, skeleton
- Implement useComparison and useReports hooks

QA (@qa-engineer):
- Setup Playwright E2E testing framework
- Create 7 test spec files with 94 test cases
- Add visual regression testing with baselines
- Configure multi-browser testing (Chrome, Firefox, WebKit)
- Add mobile responsive tests
- Create test fixtures and helpers
- Setup GitHub Actions CI workflow

Documentation (@spec-architect):
- Create detailed kanban-v0.4.0.md with 27 tasks
- Update progress.md with v0.4.0 tracking
- Create v0.4.0 planning prompt

Features:
✅ PDF/CSV Report Generation
✅ Interactive Charts (Pie, Area, Bar)
✅ Scenario Comparison (2-4 scenarios)
✅ Dark/Light Mode Toggle
✅ E2E Test Suite (94 tests)

Dependencies added:
- Backend: reportlab, pandas, slowapi
- Frontend: recharts, date-fns, @radix-ui/react-checkbox/dialog/tabs
- Testing: @playwright/test

27 tasks completed, 100% v0.4.0 implementation

frontend/e2e/setup-verification.spec.ts

@@ -0,0 +1,129 @@
+/**
+ * E2E Test: Setup Verification
+ * 
+ * This test file verifies that the E2E test environment is properly configured.
+ * Run this first to ensure everything is working correctly.
+ */
+
+import { test, expect } from '@playwright/test';
+import { navigateTo, waitForLoading } from './utils/test-helpers';
+
+test.describe('E2E Setup Verification', () => {
+  test('frontend dev server is running', async ({ page }) => {
+    await navigateTo(page, '/');
+    
+    // Verify the page loads
+    await expect(page.locator('body')).toBeVisible();
+    
+    // Check for either dashboard or loading state
+    const bodyText = await page.locator('body').textContent();
+    expect(bodyText).toBeTruthy();
+    expect(bodyText!.length).toBeGreaterThan(0);
+  });
+
+  test('backend API is accessible', async ({ request }) => {
+    // Try to access the API health endpoint or scenarios endpoint
+    const response = await request.get('http://localhost:8000/api/v1/scenarios', {
+      timeout: 10000,
+    });
+
+    // Should get 200 OK
+    expect(response.status()).toBe(200);
+    
+    // Response should be JSON
+    const contentType = response.headers()['content-type'];
+    expect(contentType).toContain('application/json');
+    
+    // Should have expected structure
+    const data = await response.json();
+    expect(data).toHaveProperty('items');
+    expect(data).toHaveProperty('total');
+    expect(Array.isArray(data.items)).toBe(true);
+  });
+
+  test('CORS is configured correctly', async ({ request }) => {
+    const response = await request.get('http://localhost:8000/api/v1/scenarios', {
+      headers: {
+        'Origin': 'http://localhost:5173',
+      },
+    });
+
+    // Check CORS headers
+    const corsHeader = response.headers()['access-control-allow-origin'];
+    expect(corsHeader).toBeTruthy();
+  });
+
+  test('all required browsers are available', async ({ browserName }) => {
+    // This test will run on all configured browsers
+    // If it passes, the browser is properly installed
+    expect(['chromium', 'firefox', 'webkit']).toContain(browserName);
+  });
+
+  test('screenshots can be captured', async ({ page }) => {
+    await navigateTo(page, '/');
+    await waitForLoading(page);
+
+    // Take a screenshot
+    const screenshot = await page.screenshot();
+    
+    // Verify screenshot is not empty
+    expect(screenshot).toBeTruthy();
+    expect(screenshot.length).toBeGreaterThan(0);
+  });
+
+  test('localStorage and sessionStorage work', async ({ page }) => {
+    await navigateTo(page, '/');
+
+    // Test localStorage
+    await page.evaluate(() => {
+      localStorage.setItem('e2e-test', 'test-value');
+    });
+
+    const localValue = await page.evaluate(() => {
+      return localStorage.getItem('e2e-test');
+    });
+
+    expect(localValue).toBe('test-value');
+
+    // Clean up
+    await page.evaluate(() => {
+      localStorage.removeItem('e2e-test');
+    });
+  });
+
+  test('network interception works', async ({ page }) => {
+    // Intercept API calls
+    const apiCalls: string[] = [];
+    
+    await page.route('**/api/**', async (route) => {
+      apiCalls.push(route.request().url());
+      await route.continue();
+    });
+
+    await navigateTo(page, '/');
+    await waitForLoading(page);
+
+    // Verify we intercepted API calls
+    expect(apiCalls.length).toBeGreaterThan(0);
+  });
+});
+
+test.describe('Environment Variables', () => {
+  test('required environment variables are set', () => {
+    // Verify CI environment if applicable
+    if (process.env.CI) {
+      expect(process.env.CI).toBeTruthy();
+    }
+  });
+
+  test('test data directories exist', async () => {
+    const fs = require('fs');
+    const path = require('path');
+
+    const fixturesDir = path.join(__dirname, 'fixtures');
+    const screenshotsDir = path.join(__dirname, 'screenshots');
+
+    expect(fs.existsSync(fixturesDir)).toBe(true);
+    expect(fs.existsSync(screenshotsDir)).toBe(true);
+  });
+});