Add SDK account diagnostics report

[El-swaggerito]

Description

Difficulty: Expert

Type: Feature

Summary

Add an account diagnostics report for SDK consumers.

Current Behaviour

Applications may not have a single safe way to diagnose account state, network state, configuration, and payment readiness.

Expected Behaviour

The SDK should expose a redacted diagnostics report suitable for support and debugging.

Suggested Implementation

Create diagnostics types, account checks, config checks, network checks, redaction, tests, and docs.

Files or Areas Likely Affected

• src/accounts/
• src/diagnostics/
• src/config/
• src/network/
• tests/
• docs/

Acceptance Criteria

• Account diagnostics report is implemented.
• Account, network, and config states are represented.
• Sensitive data is redacted.
• Payment readiness is referenced where appropriate.
• Tests verify healthy and failing diagnostics.
• Docs explain safe sharing of diagnostics.

Additional Notes

Diagnostics must not expose secrets.