feat(#10976): qualifiers for contacts by reference

[witash]

Description

Adds byShortcodes and byExternalRefs qualifiers to cht-datasource over medic-client/contacts_by_reference, and exposes them as shortcode / external_ref params on GET /api/v1/contact/uuid and GET /api/v1/contact. Follows the byPhones pattern from #11249. No existing contacts_by_reference caller is migrated (that's #11443).

• byShortcodes matches verbatim. byExternalRefs upper-cases its input to match the view's rc_code.toUpperCase(). A hand-built lower-case qualifier fails the guard.
• Local: phones, shortcodes and external refs share one keyed-view helper. Both the uuid and doc paths filter through isContact (the view emits national_office and unconfigured type: contact docs). Both paths also return each contact at most once per page, since a contact with both patient_id and place_id in the supplied list is emitted twice.
• The existing assert helpers are extended to accept the new shapes rather than duplicated. They keep their ...Phones... names.
• Precedence on /uuid is phone, then shortcode, then external_ref, then type/freetext. On /contact, ids comes before all of them.
• The only change visible to existing API users is the no-qualifier 400 message, which now lists the new params.

closes #10976

Code review checklist

• UI/UX backwards compatible: Test it works for the new design (enabled by default). And test it works in the old design, enable can_view_old_navigation permission to see the old design. Test it has appropriate design for RTL languages.
• Readable: Concise, well named, follows the style guide
• Documented: Configuration and user documentation on cht-docs
• Tested: Unit and/or e2e where appropriate
• Internationalised: All user facing text
• Backwards compatible: Works with existing data and configuration or includes a migration. Any breaking changes documented in the release notes.
• AI disclosure: Please disclose use of AI per the guidelines.

Compose URLs

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• Core
• CouchDB Single
• CouchDB Cluster

License

The software is provided under AGPL-3.0. Contributions to this project are accepted under the same license.