SEC-520: npm registry token exposure

[Shasheen8]

Security Fix: NPM Registry Token Exposure

Issue: NPM registry authentication tokens were exposed in the DOM on the Custom NPM Registry settings page, accessible to all workspace members including read-only users (SEC-520).

Changes:

• Modified NpmRegistry type
• Updated compile.ts to handle the boolean flag instead of the actual token
• Removed client-side token handling from NPM registry fetcher

Impact:

• Auth tokens are no longer sent to the client
• Client only receives a boolean indicating if a token is configured
• Tokens cannot be extracted from DOM, network requests, or browser storage
• NPM package fetching continues to work as authentication is handled server-side

This fix will ensures sensitive NPM registry credentials remain server-side only, preventing unauthorized access by workspace members with limited permissions.

Associated tickets:

1. SEC-520
2. ENG-39975