[FEATURE] Implement handle_authentication skill

[edenreich]

Summary

Implement the handle_authentication skill to provide comprehensive authentication handling functionality. This skill allows the agent to handle various authentication methods including basic auth, form-based login, and OAuth flows.

Acceptance Criteria

• Support HTTP basic authentication
• Implement form-based login automation
• Handle OAuth authentication flows
• Support custom login page navigation
• Implement configurable field selectors for login forms
• Handle two-factor authentication prompts
• Support session persistence and cookies
• Implement authentication failure detection
• Handle CAPTCHA detection and reporting
• Add secure credential handling (no logging)
• Support authentication state verification
• Add unit tests covering various authentication scenarios