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/fixtures/test-scenarios.ts

@@ -0,0 +1,76 @@
+/**
+ * Test Scenarios Fixtures
+ * 
+ * Sample scenario data for E2E testing
+ */
+
+export interface TestScenario {
+  id: string;
+  name: string;
+  description: string;
+  tags: string[];
+  region: string;
+  status: 'draft' | 'running' | 'completed' | 'archived';
+}
+
+export const testScenarios: TestScenario[] = [
+  {
+    id: 'test-scenario-001',
+    name: 'E2E Test Scenario - Basic',
+    description: 'A basic test scenario for E2E testing',
+    tags: ['e2e', 'test', 'basic'],
+    region: 'us-east-1',
+    status: 'draft',
+  },
+  {
+    id: 'test-scenario-002',
+    name: 'E2E Test Scenario - Running',
+    description: 'A running test scenario for E2E testing',
+    tags: ['e2e', 'test', 'running'],
+    region: 'eu-west-1',
+    status: 'running',
+  },
+  {
+    id: 'test-scenario-003',
+    name: 'E2E Test Scenario - Completed',
+    description: 'A completed test scenario for E2E testing',
+    tags: ['e2e', 'test', 'completed'],
+    region: 'ap-southeast-1',
+    status: 'completed',
+  },
+  {
+    id: 'test-scenario-004',
+    name: 'E2E Test Scenario - High Volume',
+    description: 'A high volume test scenario for stress testing',
+    tags: ['e2e', 'test', 'stress', 'high-volume'],
+    region: 'us-west-2',
+    status: 'draft',
+  },
+  {
+    id: 'test-scenario-005',
+    name: 'E2E Test Scenario - PII Detection',
+    description: 'A scenario for testing PII detection features',
+    tags: ['e2e', 'test', 'pii', 'security'],
+    region: 'eu-central-1',
+    status: 'draft',
+  },
+];
+
+export const newScenarioData = {
+  name: 'New E2E Test Scenario',
+  description: 'Created during E2E testing',
+  tags: ['e2e', 'automated'],
+  region: 'us-east-1',
+};
+
+export const updatedScenarioData = {
+  name: 'Updated E2E Test Scenario',
+  description: 'Updated during E2E testing',
+  tags: ['e2e', 'automated', 'updated'],
+};
+
+export const comparisonScenarios = [
+  'test-scenario-002',
+  'test-scenario-003',
+  'test-scenario-004',
+];