chore(bedrock): add Cohere Embed v4 multimodal embeddings model (#35665)

Add a new mode.

* [Cohere’s Embed v4 multimodal embeddings model now available on Amazon Bedrock](https://aws.amazon.com/about-aws/whats-new/2025/10/coheres-embed-v4-multimodal-embeddings-bedrock/)


### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: mazyu36

packages/aws-cdk-lib/aws-bedrock/lib/foundation-model.ts

@@ -305,6 +305,9 @@ export class FoundationModelIdentifier {
   /** Base model "cohere.embed-multilingual-v3:0:512". */
   public static readonly COHERE_EMBED_MULTILINGUAL_V3_0_512 = new FoundationModelIdentifier('cohere.embed-multilingual-v3:0:512');
 
+  /** Base model "cohere.embed-v4:0". */
+  public static readonly COHERE_EMBED_V4 = new FoundationModelIdentifier('cohere.embed-v4:0');
+
   /** Base model "deepseek.r1-v1:0". */
   public static readonly DEEP_SEEK_R1_V1_0 = new FoundationModelIdentifier('deepseek.r1-v1:0');