feat(provider): add AI Badgr OpenAI-compatible provider

[ghost]

Description: (required)

• Added AI Badgr to the global provider registry
• Implemented OpenAI-compatible chat completion and streaming support
• Added provider-specific API configuration (base_url, auth headers)
• Included a usage notebook demonstrating Portkey + AI Badgr integration

Tests Run/Test cases added: (required)

• Manual verification via OpenAI client and Portkey client
• Streaming responses validated using chunk transformation logic

Type of Change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)