Complete E2E test implementation with comprehensive reliability fixes

- Implement Priority 1 E2E test coverage for critical user journeys:
  * Group lifecycle management (creation, navigation, editing)
  * Basic expense management (create, view, edit, delete)
  * Balance calculation and verification
  * Multiple expense scenarios and split calculations

- Add comprehensive reliability infrastructure:
  * ReliabilityUtils class with retry mechanisms and enhanced navigation
  * Page Object Model (POM) architecture for maintainable tests
  * Test data management utilities with unique identifiers
  * Enhanced Playwright configuration with increased timeouts and retries

- Fix all flaky test issues:
  * Add required test IDs to UI components for reliable element targeting
  * Implement multiple fallback strategies for element selection
  * Enhanced tab navigation with URL verification and retry logic
  * Proper wait strategies for network idle states and dynamic content

- Test results: 39/39 tests passing (100% success rate) across all browsers

🤖 Generated with [Claude Code](https://claude.ai/code)

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

tests/pom/create-group-page.ts

@@ -5,6 +5,7 @@ export class CreateGroupPage {
 
   async navigate() {
     await this.page.goto('http://localhost:3002/groups/create')
+    await this.page.waitForLoadState('networkidle')
   }
 
   async fillGroupName(name: string) {
@@ -29,5 +30,7 @@ export class CreateGroupPage {
 
   async submit() {
     await this.page.getByRole('button', { name: 'Create' }).click()
+    // Wait for navigation to complete
+    await this.page.waitForLoadState('networkidle')
   }
 }