Podcast, show and episode pages after the design, on the show-and-episodes model

Problem/Motivation

The podcast pages in The Rightup do not follow the design. The Podcasts page shows static cards, and there is no real show page or episode page.

The design treats a Podcast as a show and a Podcast episode as belonging to one show. The site template should build its pages on that model.

Steps to reproduce

1. Install The Rightup from 1.0.x-dev.
2. Open the Podcasts page, a podcast and an episode, and compare them with the design.

Proposed resolution

• Podcasts page: list the shows from the podcasts view, with episode counts and the design's grid.
• Show page: header with cover and episode count, the show's episodes with an AJAX "View More Episodes", and More Podcasts.
• Episode page: episode number, title, "Listen on" links, audio player, date and time, share, "Hosted and Written by", details, the transcript collapsed behind Read More, a More Episodes rail with View All, the newsletter band and More Podcasts.
• Demo content: 6 shows and 67 dated episodes, each episode in exactly one show. Share row set to Facebook, X, Instagram and copy link.

Checked on a fresh install in a real browser: all podcast pages render, load more works, and axe-core reports 0 WCAG 2.2 AA violations on the listing, show and episode pages at 390px and 1440px.

Depends on #3622954: A podcast is a show with episodes: add the Podcast episode content type and the views that list both (Varbase Podcasts Base). Related: #3627494: Podcast, show and episode pages: view rows, Read more, platform links and the design's hover and focus states (theme side, merged) and #3627367: Podcasts page disables the card's content padding and stacks two cards per column, so the card content touches the next card (its MR !59 work is included here).

AI-Generated: Yes

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
• ✅ Open the MR
• ❌ More Podcasts is a static three-card grid, not the design's carousel
• ❌ Demo platform links point at each platform's home page (RSS at the site feed)
• ❌ The host name is plain text, as no host page exists

User interface changes

• New Podcasts listing, show and episode pages after the design.

API changes

• N/A

Data model changes

• Uses the Podcast episode content type from Varbase Podcasts Base. An episode references one podcast.

Release notes snippet

• N/A