Add AWS Bedrock Support

**Description:**

Open Lovable currently supports connecting to several AI model providers (e.g., OpenAI, Anthropic, Ollama). We’d like to add integration for **AWS Bedrock**, allowing users to query models hosted on Bedrock directly from the Lovable interface.

**Acceptance Criteria:**

* [ ] Add a new provider option in the settings for AWS Bedrock.
* [ ] Allow users to configure AWS credentials (Access Key, Secret Key, Region) and select the Bedrock model (e.g., Claude, Titan, Mistral).
* [ ] Support both streaming and non-streaming responses from Bedrock.
* [ ] Respect existing conversation/session handling patterns in Lovable.
* [ ] Document the setup process, including necessary AWS IAM permissions and example configuration.

**References:**

* [[AWS Bedrock API Documentation]](https://docs.aws.amazon.com/bedrock/)
* [[AWS SDK for JavaScript v3 – Bedrock Runtime]](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-bedrock-runtime/)

**Why:**

Adding AWS Bedrock support would enable Lovable users to take advantage of models hosted on AWS, benefiting from enterprise-grade security, compliance, and private networking capabilities without leaving the Open Lovable environment.