Update GitHub Actions workflows to use Playwright container

[tataihono]

Update GitHub Actions workflows to use Playwright container image instead of specific runner types.

Changes

• Updated app-deploy.yml, e2e-tests.yml, and ecs-frontend-deploy-stage.yml workflows
• Changed from specific runner types (blacksmith-4vcpu-ubuntu-2204, blacksmith-2vcpu-ubuntu-2204) to generic blacksmith runner with Playwright container
• Added Playwright container configuration with environment variables
• Removed Playwright browser caching steps (browsers are pre-installed in container)

[linear]

ENG-3550