feat(providers): add JWT Bearer Authorization provider

[TarasSpashchenko]

Summary

Adds JWT Bearer Authorization as a new authentication provider for CodeMie CLI. Users can now configure JWT-based authentication where tokens are provided at
runtime via CLI or environment variables, rather than during setup. This is ideal for environments with external token management systems, CI/CD pipelines, or
testing scenarios.

Changes

• New bearer-auth provider with simplified setup (only asks for API URL, token provided later)
• JWT authentication proxy plugin with Bearer token injection and expiration validation
• --jwt-token CLI option added to all agent commands for runtime token provision
• JWT health check added to codemie doctor for token validation and expiration monitoring
• All agents (Claude, Gemini, OpenCode, CodeMie Code) now support bearer-auth provider
• Shared URL normalization utility (ensureApiBase) for consistent /code-assistant-api suffix handling
• JWT credential storage with AES-256-CBC encryption matching SSO security standards
• Configuration follows SSO pattern with codeMieUrl (user input) and baseUrl (full API URL)
• Comprehensive documentation in docs/AUTHENTICATION.md with setup, usage examples, and troubleshooting

Impact

Before:

# Only SSO authentication
codemie setup  # Browser-based flow
codemie-claude "analyze code"

After:

# New JWT option during setup
codemie setup
? Choose provider: Bearer Authorization
? CodeMie base URL: https://codemie.lab.epam.com
✓ Configuration saved

Provide token at runtime

export CODEMIE_JWT_TOKEN="eyJhbG..."
codemie-claude "analyze code"

Or via CLI

codemie-claude --jwt-token "eyJhbG..." "analyze code"

Users benefit from simplified setup for JWT environments and flexible token management at runtime.

Checklist

• Self-reviewed
• Manual testing performed
• Documentation updated
• No breaking changes