Create SDK advanced architecture map

[El-swaggerito]

Description

Difficulty: Expert

Type: Documentation

Summary

Create an advanced architecture map for SDK modules and boundaries.

Current Behaviour

New contributors may not understand how wallet, payments, transactions, Soroban, vault, config, and errors fit together.

Expected Behaviour

The repository should document module boundaries and dependency direction.

Suggested Implementation

Add an architecture map with diagrams or structured notes explaining modules, responsibilities, and dependency rules.

Files or Areas Likely Affected

docs/
README.md
src/

Acceptance Criteria

• Architecture map is added.
• Module responsibilities are explained.
• Dependency boundaries are documented.
• Security-sensitive modules are highlighted.
• README links to the map.

Additional Notes

This improves long-term maintainability.

[Mubking-dev]

Hi, I'm Mubarak — a Full-Stack & Blockchain Developer with 3+ years of experience. I've reviewed this issue and I'm confident I can handle it. I'll submit a clean PR within 2–3 days. Please assign it to me!

[grantfox-oss]

🦊 GrantFox — @Mubking-dev has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #223)
2. Your PR will be reviewed by the Axionvera maintainers

Good luck! Track your progress on GrantFox.