Show release plans missing Product Type in dashboard admin view

## Problem

The release plan dashboard admin view has a **Missing Product Details** group, but it currently only detects release plans without a Product ID. The dashboard does not fetch or map `Custom.ProductType`.

As a result, release plans with a Product ID but no Product Type are not visible for proactive remediation and can later fail CPEX KPI attestation. This complements the legacy-data cleanup tracked by #16704.

## Proposed solution

- Add `Custom.ProductType` to the release plan fields fetched from Azure DevOps and map it to the normalized dashboard payload.
- Add a **Missing Product Type** group under **Needs Attention** in the admin view.
- Include release plans with a nonempty Product ID and an empty or whitespace-only Product Type.
- Keep release plans without a Product ID in the existing **Missing Product Details** group so plans are not double-counted.
- Display the section count and existing release-plan cards with links to the corresponding ADO work items.
- Preserve the dashboard's existing filtering of test release plans.

## Acceptance criteria

- [ ] `Custom.ProductType` is included in the normalized dashboard payload.
- [ ] The admin view identifies release plans whose Product ID is present but Product Type is empty or whitespace-only.
- [ ] Release plans without Product IDs remain in **Missing Product Details** and are not double-counted.
- [ ] Test-tagged release plans remain excluded consistently.
- [ ] Tests cover ADO field mapping, group membership, section count, and admin-view layout.

No files or test paths are named. Start by locating the Azure DevOps release-plan field mapping and normalized dashboard payload, then trace the admin view's existing Missing Product Details grouping and related tests. Done means Product Type mapping, exclusive group membership, test-plan filtering, section counts, cards, links, and layout are covered by tests.

Written by the indexing model from the issue text.