Make the Live feed and Search views follow the interface language

Problem/Motivation

The Rightup has no second language, so two things that only show once a second language is installed were never exercised.

• The Live feed view (live_feed) lists every translation of a news article or episode. On a site with Arabic, the English home page ticker shows Arabic items and the Arabic home page shows both languages.
• The Search view lists results of every language. An Arabic keyword on the English search page returns Arabic results, and the other way round.

Steps to reproduce

1. Install The Rightup, then add a language with translated news (for example Arabic).
2. Open the English home page and read the ticker under the header: Arabic titles appear. Open /search?keywords=%D8%B9%D9%85%D8%A7%D8%B1%D8%A9 on the English site: Arabic results appear.

Proposed resolution

• views.view.live_feed: add the same langcode filter the other Rightup views already carry (interface language, plus und and zxx).
• views.view.search: add a Search API search_api_language filter with the same values.

A single-language site is unaffected: every item is in the interface language, so both filters match everything.

Remaining tasks

• ✅ File an issue
• ✅ Addition/Change/Update/Fix
• ❌ Testing to ensure no regression
• ❌ Automated unit/functional testing coverage
• ➖ Developer Documentation support
• ➖ User Guide Documentation support
• ➖ UX/UI designer responsibilities
• ❌ Accessibility and Readability
• ❌ Reviewed by a human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ❌ Update Release Notes
• ❌ Release

User interface changes

• None on a single-language site. On a multilingual site the ticker and the search results follow the interface language.

API changes

• N/A

Data model changes

• Two view filters added. No new config entities.

Release notes snippet

• The Live feed and Search views follow the interface language on multilingual sites,.

AI-Generated: Yes. Drafted and tested with Claude Code, reviewed by the contributor.