docs: Scaffold official documentation site (#996)

[Majdi-Zlitni]

Documentation Refactoring Summary

1. Created design-decisions.md

The sections "Goals", "Design Decisions and Dependencies", and "Patterns Used" were extracted from the large root README.md and moved into a dedicated file: design-decisions.md.

This document now explains why specific architectural choices were made, such as the use of:

• FastEndpoints
• Mediator
• Entity Framework Core
• Other supporting libraries and patterns

Separating these decisions makes the architecture easier to understand and maintain.

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2. Created getting-started.md

All setup instructions and development guidance were moved from the root README.md into a new file: getting-started.md.

This includes:

• CLI commands for project setup
• Template comparisons (Full vs Minimal)
• Instructions for adding Controllers or Razor Pages

This keeps the onboarding documentation focused and easier for new developers to follow.

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3. Simplified the Root README.md

The root README.md was trimmed to remove the detailed getting started and architecture explanations.

Instead, it now ends with a clear Documentation section directing users to the official resources.