Add SDK method deprecation warning system

[Kingsman-99]

Label: complexity: high
Points: 200

Description

As the SDK evolves (e.g. pay_with_memo vs. newer patterns), there's no consistent way to warn integrators they're using a soon-to-be-removed method, beyond ad hoc code comments.

Technical Context

New src/deprecation.ts. deprecated(methodName, { removedInVersion, alternative }) decorator/wrapper applied to selected exported functions; logs a one-time-per-method console warning (via Issue 12's logger if present, else console.warn) on first call.

Acceptance Criteria

• Wrapped methods still function identically — only adds a warning side effect
• Warning fires once per method per process (not on every call) to avoid log spam
• Warning message includes the suggested alternative
• Tests: warning fires exactly once across multiple calls; message contains the alternative text

---

[Glam26]

I'd be happy to take this on.

I've worked on similar issues across multiple open-source and production projects, including feature development, refactoring, testing, documentation, performance improvements, and bug fixes. My approach is to first understand the existing architecture and conventions, then deliver a solution that is clean, maintainable, and aligned with the project's standards.

I'll make sure the implementation is thoroughly tested, well-documented where necessary, and covers relevant edge cases. I'm comfortable collaborating during review, incorporating feedback quickly, and ensuring the final result is production-ready.

[Glam26]

I'd be happy to take this on.

I've worked on similar issues across multiple open-source and production projects, including feature development, refactoring, testing, documentation, performance improvements, and bug fixes. My approach is to first understand the existing architecture and conventions, then deliver a solution that is clean, maintainable, and aligned with the project's standards.

I'll make sure the implementation is thoroughly tested, well-documented where necessary, and covers relevant edge cases. I'm comfortable collaborating during review, incorporating feedback quickly, and ensuring the final result is production-ready.