Modernize CI/CD pipeline with comprehensive automation (#25)

* Initial plan

* Add comprehensive CI/CD workflows and tooling

- Add PR validation workflow with lint, format, type check, test, and build steps
- Improve Docker build workflow with caching, security scanning, and manual trigger
- Add CodeQL security analysis workflow
- Add Dependabot configuration for automated dependency updates
- Configure ESLint with TypeScript support
- Add npm scripts for linting and formatting
- Format code with Prettier
- Fix linting issues in source code

Co-authored-by: THoguet <61246905+THoguet@users.noreply.github.com>

* Update README and fix build configuration

- Add CI/CD documentation to README
- Document code quality tools and scripts
- Disable font optimization in production build to avoid network dependency
- Add build cache configuration for GitHub Actions

Co-authored-by: THoguet <61246905+THoguet@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: THoguet <61246905+THoguet@users.noreply.github.com>

src/app/services/user-input-service.ts

@@ -1,4 +1,4 @@
-import { Injectable, signal, PLATFORM_ID, inject } from '@angular/core';
+import { Injectable, signal } from '@angular/core';
 import { VacationsNumber } from './calendar-service';
 
 @Injectable({