Add comprehensive unit tests for components and services

[devin-ai-integration]

Add comprehensive unit tests for components and services

Summary

This PR adds unit tests to improve test coverage across the Angular demo project:

• ItemComponent: Tests for @input properties (name, description, price) and the like() method including button click interaction
• UsersServices: Completed HTTP mocking tests for getUsers() (previously marked as TODO)
• AddItemComponent: Granular form validation tests for individual fields and tests for formInit/saveItem methods
• UsersComponent: DOM rendering tests and console logging verification

Review & Testing Checklist for Human

• Verify all tests pass in CI - Tests could not be run locally due to ChromeHeadless/OpenSSL compatibility issues with the environment's Node.js version
• Review UsersServices HTTP mocking tests - verify the mock URL matches the actual service URL (https://jsonplaceholder.typicode.com/users)
• Check that DOM queries in UsersComponent tests (e.g., By.css('button'), By.css('li')) correctly target the expected elements
• Verify the any type casting in UsersServices.service.spec.ts is acceptable (used to work around TypeScript's Object type inference)

Recommended test plan: Run ng test locally or wait for CI to confirm all 30+ tests pass.

Notes

• The project has pre-existing build errors unrelated to these changes (ItemComponent @input binding issues in templates)
• Removed the "TODO: test sin terminar" comment from UsersServices.service.spec.ts as the tests are now complete

Link to Devin run: https://app.devin.ai/sessions/6aa652700ad34aab8f9adae17a020e13
Requested by: milind@cognition.ai (@milind-cognition)

[devin-ai-integration]

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