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/components/user-input/user-input.ts

@@ -1,7 +1,7 @@
 import { Component, OnInit, OnDestroy, effect } from '@angular/core';
 import { MatFormField, MatLabel } from '@angular/material/form-field';
 import { MatInputModule } from '@angular/material/input';
-import { FormControl, FormGroup, ReactiveFormsModule, Validators } from '@angular/forms';
+import { FormControl, FormGroup, ReactiveFormsModule } from '@angular/forms';
 import { UserInputService } from '../../services/user-input-service';
 import { VacationsNumber } from '../../services/calendar-service';
 import { debounceTime, takeUntil, Subject } from 'rxjs';