Keep YouTube fallbacks small enough to review

The first baseline committed the raw YouTube API dump, which fixed clean builds but carried unused API metadata. The route fallback only needs prebuilt listing objects, so this replaces the raw seed with slug-keyed listing fallbacks and adds a refresh script that fetches the latest source data before projecting it.

Constraint: helpers/site-listings.js must work in a fresh checkout before generated static/api output exists

Rejected: Commit the full raw YouTube JSON | unnecessarily large and mostly unused by the fallback path

Rejected: Drop descriptions only | smaller but would weaken app-link and tag matching semantics

Confidence: high

Scope-risk: narrow

Reversibility: clean

Directive: Refresh static/api/youtube-video-listings.json via scripts/update-youtube-video-listing-fallbacks.js, not by committing static/api/youtube-videos.json

Tested: pnpm run with-env vite-node scripts/update-youtube-video-listing-fallbacks.js

Tested: pnpm run with-env vitest test/prebuild/site-listings.test.js

Tested: pnpm run netlify-prebuild:test-prebuild-functions

Tested: pnpm run netlify-prebuild

static/api/.gitignore

@@ -1,3 +1,3 @@
 *
 !.gitignore
-!youtube-videos.json
+!youtube-video-listings.json