docs: establish project intent, architecture, and evolution docs

[lucaspaiva-lp]

Summary

This PR adds the foundational documentation for the project, defining its intent, boundaries, and architectural direction.

---

What was added

• Project README clarifying purpose, scope, and non-goals
• Architecture documentation describing the layered (MVC-inspired) design
• Scope definition to prevent responsibility creep
• Initial changelog documenting early architectural and testing decisions

---

Why

• Align implementation with explicit architectural intent
• Serve as a reference for future decisions and refactors
• Ensure consistency as the project evolves beyond its initial phase

---

Notes

• The architecture reflects the current stage of the project and will evolve
• Documentation prioritizes clarity and correctness over completeness
• Inspired by Clean Code principles (Rocketseat), with intentional adaptations