feat: add comprehensive testing setup with Playwright and Bruno

[Thilina2468]

• Add Playwright for end-to-end testing of user flows
• Add Bruno collections for API route testing
• Create foundation API routes (/health, /firebase-test, /hello)
• Add E2E tests for homepage and basic functionality
• Update GitHub Actions to run Playwright tests
• Update documentation with testing guidelines and examples

[Copilot]

Pull Request Overview

This PR adds comprehensive testing infrastructure to the task manager project, including end-to-end testing with Playwright and API testing with Bruno collections. The changes establish foundation API routes and CI/CD integration to ensure code quality and functionality verification.

• Implements Playwright for end-to-end testing of user flows and basic application functionality
• Adds Bruno collections for API route testing with health checks and Firebase connectivity validation
• Creates foundation API endpoints (/health, /firebase-test, /hello) to support testing infrastructure

Reviewed Changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/e2e/*.spec.ts	Playwright test files for homepage functionality and foundation API testing
src/lib/firebaseAdmin.ts	New Firebase Admin SDK configuration for server-side operations
src/lib/firebase.ts	Enhanced Firebase client configuration with RTDB support and initialization checks
src/app/api/*/route.ts	Foundation API routes for health checks, Firebase testing, and hello endpoints
playwright.config.ts	Playwright configuration with multi-browser testing and CI setup
package.json	Added testing dependencies and scripts for Playwright
bruno/	Bruno API test collections for endpoint validation
.github/workflows/tests.yml	CI/CD pipeline configuration for automated testing
README.md	Comprehensive testing documentation and usage guidelines

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