🤖 feat: Add support for Amazon Bedrock

Add Amazon Bedrock as a supported AI provider using @ai-sdk/amazon-bedrock.

This enables enterprise users to use AWS-hosted models including:
- Claude models (via Anthropic on Bedrock)
- Amazon Nova models
- Meta Llama models
- Mistral models
- And other Bedrock-supported models

Configuration in providers.jsonc:
{
  "bedrock": {
    "region": "us-east-1",
    "accessKeyId": "...",
    "secretAccessKey": "..."
  }
}

Model string format: bedrock:<model-id>
Example: bedrock:anthropic.claude-3-5-sonnet-20241022-v2:0

Closes #764

Author: ibetitsmike