Add constructor parameter validation

[meshackyaro]

Description

SDK constructor performs async validation causing unhandled promise rejections. Constructors should be synchronous.

Component

SDK

Difficulty

🟡 Medium

Tasks

• Move async logic out of constructor
• Add separate async init() method
• Validate synchronously in constructor
• Update initialization documentation
• Add init pattern examples

Acceptance Criteria

• Constructor is synchronous
• Async initialization explicit
• No unhandled promise rejections

Estimated Time

2 days