Improve overall code structure and create examples

[ju4n97]

Note
Depends on #630

Features to be included

• Use of self-closing tags.
• Use of the new takeUntilDestroyed operator from rxjs-interop.
• Example of how to bind router information to routed component inputs.
• Examples of using reactive forms, HTTP client, and image optimization.
• Examples of the new required inputs feature.
• Creation of auth directives.
• Clean up the project by removing unused/outdated code.
• Thorough use of the new Angular reactivity system: Angular Signals.
• Simplify implementation of the ThemeService and the storage utility.