Check XBull extension version before attempting connection

[Kingsman-99]

Description

XBullAdapter connects to the XBull browser extension without verifying the extension version. Older extension versions do not support the current API surface, causing cryptic runtime errors.

Acceptance Criteria

• Before connecting, the adapter reads window.xBullSDK.version or equivalent
• Versions below MIN_XBULL_VERSION (export this constant) reject with an ExtensionVersionError listing the required version
• Compatible versions proceed with the existing connection flow
• Unit tests pass

Context

• Target file: src/wallets/adapters/XBullAdapter.ts
• Set MIN_XBULL_VERSION to the first version that supports the current API