[ECS] : ECS Service Connect integration with VPC Lattice

### Community Note

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**Tell us about your request**
Seamless cross-VPC communication for service with VPC Lattice integration

**Which service(s) is this request for?**
ECS Service Connect

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.

**Are you currently working around this issue?**
Researching

**Additional context**
Anything else we should know?

**Attachments**
If you think you might have additional information that you'd like to include via an attachment, please do - we'll take a look. (Remember to remove any personally-identifiable information.)

The issue names ECS Service Connect and VPC Lattice but does not identify repository files, tests, entry points, or a concrete implementation scope. Start by clarifying the desired cross-VPC behavior and acceptance criteria with maintainers; no completion check or validation path is provided.

Written by the indexing model from the issue text.