Feature Request: Clarify supported Node.js and runtime environments

### Is your feature request related to a problem? Please describe.

The `base/account-sdk` documentation does not clearly state which Node.js versions or runtime environments are officially supported. This can cause uncertainty during setup and CI configuration.

### Problem Description
Developers may be unsure whether the SDK supports specific Node.js versions, serverless runtimes, or edge environments, leading to trial-and-error during integration.

### Proposed Solution
Add a short section to the README listing supported Node.js versions and any known limitations or recommendations for runtimes (e.g., serverless, edge).

### Acceptance Criteria
The README clearly lists supported Node.js versions and runtime notes. Developers can configure their environments confidently without testing unsupported setups.

Start with the account-sdk README and verify the project's current Node.js requirements and runtime assumptions before editing. Add a concise section covering supported Node.js versions, serverless or edge runtime notes, and known limitations; done means developers can configure their environments without trial and error.

Written by the indexing model from the issue text.