Issue: feat(router): Add `eligible_connector` to PML response (v2)

We need to return `eligible_connector` in PML response, required by SDK

Resolution: <think>
PR Context:
- Title: feat(router): Return eligible_connector in PML for payment (v2)
- Merged: None
- Files changed: 3 files
- Commits: 2 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [x] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
Add `eligible_connector` in PML response

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

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</think>

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