#26278 fix(websocket): forward URL credentials as Authorization header

Summary

• Extracts credentials from WebSocket URL (ws://user:pass@host) and sends them as Basic Authorization header
• User-provided Authorization header takes precedence over URL credentials
• Credentials are properly URL-decoded before being Base64-encoded

Fixes #24388

Test plan

• Added regression test test/regression/issue/24388.test.ts with 5 test cases:
  • Basic credentials in URL
  • Empty password
  • No credentials (no header sent)
  • Custom Authorization header takes precedence
  • Special characters (URL-encoded) in credentials
• Tests pass with bun bd test test/regression/issue/24388.test.ts
• Tests fail with USE_SYSTEM_BUN=1 bun test (confirming the bug existed)

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