feat(meta): rich detail calls for movies and series

movie_detail/series_detail fetch credits, videos and external ids in
one upstream request via append_to_response; cast is truncated to the
top 10 billed in the crate and a trailer is chosen by rule (official
YouTube trailer, any YouTube trailer, YouTube teaser, none).
movie_videos/series_videos serve #144's search-row chip from the
videos endpoint alone. Everything rides the existing 24h cache.

crates/arr-meta/tests/fixtures/series_videos_bluey.json

@@ -0,0 +1,7 @@
+{
+  "id": 82728,
+  "results": [
+    { "key": "bluey_clip", "site": "YouTube", "type": "Clip", "name": "Clip: Keepy Uppy", "official": true },
+    { "key": "bluey_teaser", "site": "YouTube", "type": "Teaser", "name": "Series Teaser", "official": false }
+  ]
+}