refactor: migrate validation from Joi to Zod

[CKodidela]

Description

Replaces joi with zod for all schema validation across the codebase. All schemas (base, event, filter, message, and all four payment callback schemas) have been rewritten using Zod's API. The validateSchema utility now uses safeParse instead of a try/catch cast, and the WebSocket adapter uses instanceof ZodError for proper error detection. Client-facing validation error notices are trimmed to the first issue message to avoid sending verbose Zod output.

Related Issue

Closes #455

Motivation and Context

joi was the previous validation library. This migration moves the project to zod, which has first-class TypeScript support, a cleaner API, and better type inference. The joi dependency has been removed from package.json.

How Has This Been Tested?

• All unit tests pass locally (540 passing, 0 failing) via npm run test:unit
• npm run build:check passes with no TypeScript errors
• npm run lint passes with no ESLint errors
• Tested on Node.js via WSL (Ubuntu) and Windows

Types of changes

• Non-functional change (docs, style, minor refactor)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have read the CONTRIBUTING document.
• I have added tests to cover my code changes.
• All new and existing tests passed.

[CKodidela]

@cameri it should work now, can you run checks