Add Anthropic Claude and Azure OpenAI Provider Support

[mheadd]

Currently, the LLM provider abstraction system supports Ollama (local) and OpenAI providers. To expand the multi-provider capabilities, we need to implement support for Anthropic Claude and Azure OpenAI providers.

Current State

✅ Ollama provider (fully implemented)
✅ OpenAI provider (fully implemented)
🚧 Anthropic provider (marked as "Planned" in documentation)
🚧 Azure OpenAI provider (marked as "Planned" in documentation)

Proposed Implementation

Anthropic Claude Provider

• Create api/providers/anthropic-provider.js extending the base provider interface
• Support for Claude-3 models (haiku, sonnet, opus)
• Environment variables: ANTHROPIC_API_KEY, ANTHROPIC_MODEL
• Rate limiting and error handling specific to Anthropic's API

Azure OpenAI Provider

• Create api/providers/azure-openai-provider.js extending the base provider interface
• Support for GPT models deployed on Azure
• Environment variables: AZURE_OPENAI_ENDPOINT, AZURE_OPENAI_API_KEY, AZURE_OPENAI_DEPLOYMENT_NAME
• Azure-specific authentication and endpoint handling

Environment Configuration

# Anthropic
LLM_PROVIDER=anthropic
ANTHROPIC_API_KEY=your-anthropic-key
ANTHROPIC_MODEL=claude-3-haiku-20240307

# Azure OpenAI
LLM_PROVIDER=azure-openai
AZURE_OPENAI_ENDPOINT=https://your-resource.openai.azure.com/
AZURE_OPENAI_API_KEY=your-azure-key
AZURE_OPENAI_DEPLOYMENT_NAME=your-deployment-name

Acceptance Criteria

• Both providers implement the base provider interface consistently
• Provider factory correctly instantiates new providers
• Environment configuration validation includes new providers
• All persona endpoints work identically with new providers
• Comprehensive test coverage for both providers
• Documentation updated to reflect "Ready" status
• Demo script supports testing new providers

Documentation Updates

• Update supported providers table in README.md (change 🚧 Planned to ✅ Ready)
• Add setup instructions for both providers
• Update performance comparison table with new providers
• Update .project-info.md with new provider information

Testing Requirements

• Unit tests for provider implementations
• Integration tests with mocked API responses
• Error handling tests for provider-specific failures
• Environment configuration validation tests