Security fix

Remove pydantic-ai and pin FastMCP to v2.13.3

BREAKING CHANGE: Removed pydantic-ai dependency and archived related features

Changes:

• Removed pydantic-ai dependency (security vulnerability in v<1.56.0)
• Pinned FastMCP to v2.13.3 for optimal performance
• Updated all dependencies to latest stable versions
• Archived AI-powered clients and sampling features to _Archived/
• Updated README to reflect current feature set

Why:
The security fix for pydantic-ai requires FastMCP v2.14.0+, which causes
performance issues for our use case. Since the core server doesn't need
AI agent features, we removed it for better performance and security.

Impact:
✅ Improved performance and smaller footprint
✅ All core Okta MCP server tools work as before
⚠️ CLI clients and AI sampling features moved to _Archived/

See _Archived/README.md if you need the archived features.