feat(cms): add video-subtitle content type

[lumberman]

Background

Media API defines a VideoSubtitle model with subtitle metadata keyed by videoId, edition, and languageId. Forge CMS currently does not have a matching Strapi content type stored as schema JSON, which blocks modeling this data canonically inside the Strapi repo.

Expected outcome

A new Strapi collection type named video-subtitle exists in apps/cms as schema JSON and matches the agreed CMS fields for subtitle records.

Acceptance criteria

• A new Strapi collection type video-subtitle is added under apps/cms/src/api as schema JSON.
• The collection uses collectionName: \video_subtitles`withsingularName: `video-subtitle`, pluralName: `video-subtitles`, and displayName: `Video Subtitle``.
• draftAndPublish is disabled.
• The schema includes required string fields videoId and languageId.
• The schema includes string field edition with default base.
• The schema includes text field vttSrc.
• The schema includes integer field vttVersion with default 1.
• The schema includes boolean field primary with default false.
• The schema includes enumeration field source with values ai and human, defaulting to ai.
• No extra media-api fields are added beyond the agreed CMS subset for this work item.

Possible solution(s)

1. Add apps/cms/src/api/video-subtitle/content-types/video-subtitle/schema.json following the existing Strapi content-type layout in the repo.
2. Regenerate the Strapi GraphQL schema if local CMS tooling updates apps/cms/schema.graphql as part of the content-type addition.
3. Defer uniqueness enforcement for [videoId, edition, languageId] if this bounded task is explicitly limited to schema JSON only.

References

• Media API model: VideoSubtitle
• Target bounded context: apps/cms
• Expected storage format: Strapi schema JSON in repo
• Requested CMS subset fields: videoId, languageId, edition, vttSrc, vttVersion, primary, source

[lumberman]

Execution plan:

1. Add a new Strapi collection type schema at apps/cms/src/api/video-subtitle/content-types/video-subtitle/schema.json.
2. Match only the agreed CMS subset fields from media-api: videoId, languageId, edition, vttSrc, vttVersion, primary, source.
3. Validate whether the content-type addition requires regeneration of apps/cms/schema.graphql and include it only if generated by local CMS tooling.
4. Run CMS-relevant validation for the changed files before opening a PR.