feat(plex): S5b persist rich detail + serve item/show detail from DB

Persist the info-page rich fields that were previously read LIVE from plex.metadata() on every view —
imdb_rating (IMDb-specific, vs `rating`=audienceRating), imdb_id, tagline, and full_cast
([{name,role,thumb}]) — onto plex_items/plex_shows, and serve the detail endpoints from the row.

- migration 0065: ADD imdb_rating/imdb_id/tagline/full_cast (nullable → no rewrite/lock, unlike 0064);
  NULL people_enriched_at on movie/show rows so the existing cast backfill re-fetches each once and
  fills the new columns.
- new app/plex/detail.py: rich_detail(meta) (moved out of browse._rich_meta so sync + serve share one
  parser) + apply_rich_detail(row, meta); wired into _enrich_people_batch and the info-page lazy fill.
- item_detail: movies serve cast/IMDb/tagline/genres from the row and keep plex.metadata(markers=True)
  ONLY for markers + audio/subtitle streams (so detail survives a live-Plex outage); episodes (never
  enriched) still parse detail from that live meta.
- show_detail: serves cast/IMDb from the row; `related` stays live best-effort and also lazily fills a
  not-yet-enriched show.
- tests: rich_detail/apply_rich_detail parsing + persistence, backfill stamping, item_detail
  outage-resilience + lazy fill + episode-live, show_detail row serving. Full suite 285 pass / 2 skip;
  migration verified reversible (up→down→up).

Precondition for S6's pure-DB language-aware serving.

backend/app/plex/detail.py

@@ -0,0 +1,61 @@
+"""Parse the "info page" rich metadata out of a full Plex metadata dict, and persist the subset that
+the detail endpoints serve from the DB row (E5 S5b).
+
+Shared by the live info-page path (routes.plex.browse) and the background rich re-sync (plex.sync) so
+the two never diverge — the same one-parser rule that keeps `people.py`'s cast handling consistent.
+`rich_detail` is the pure parser; `apply_rich_detail` writes the rich-ONLY fields onto a movie/show row
+(genres/directors/studio/content_rating already land from the cheap listing at `_apply_facet_fields`)."""
+
+from app.plex import people
+
+
+def rich_detail(meta: dict) -> dict:
+    """Pull the info-page extras out of a full Plex metadata dict: an IMDb score + link, content
+    rating, genres, director(s), studio, tagline, and cast (name/role/photo). Best-effort — any
+    missing field is just omitted."""
+    # Rating: prefer the explicit IMDb entry in the Rating array, else the generic audienceRating.
+    imdb_rating = None
+    for r in meta.get("Rating") or []:
+        if str(r.get("image") or "").startswith("imdb://"):
+            try:
+                imdb_rating = round(float(r.get("value")), 1)
+            except (TypeError, ValueError):
+                pass
+            break
+    if imdb_rating is None:
+        try:
+            imdb_rating = round(float(meta.get("audienceRating") or meta.get("rating")), 1)
+        except (TypeError, ValueError):
+            imdb_rating = None
+    # IMDb id (tt…) from the Guid list → a clickable link.
+    imdb_id = None
+    for g in meta.get("Guid") or []:
+        gid = str(g.get("id") or "")
+        if gid.startswith("imdb://"):
+            imdb_id = gid.split("imdb://", 1)[1]
+            break
+    return {
+        "imdb_rating": imdb_rating,
+        "imdb_id": imdb_id,
+        "imdb_url": f"https://www.imdb.com/title/{imdb_id}/" if imdb_id else None,
+        "content_rating": meta.get("contentRating"),
+        "genres": [g.get("tag") for g in (meta.get("Genre") or []) if g.get("tag")][:8],
+        "directors": [
+            d.get("tag") for d in (meta.get("Director") or []) if d.get("tag")
+        ][:4],
+        "studio": meta.get("studio"),
+        "tagline": meta.get("tagline"),
+        "cast": people.cast_from_meta(meta),
+    }
+
+
+def apply_rich_detail(row, meta: dict) -> None:
+    """Persist the rich-ONLY detail fields onto a movie/show row so the info page serves them from the
+    DB instead of a live Plex call. Call wherever a rich metadata dict is fetched (the cast backfill +
+    the info-page lazy enrich). Empty cast persists as SQL NULL (none_as_null), so an EN fallback and
+    the `full_cast IS NULL` "not yet enriched" signal stay meaningful."""
+    d = rich_detail(meta)
+    row.imdb_rating = d["imdb_rating"]
+    row.imdb_id = d["imdb_id"]
+    row.tagline = d["tagline"]
+    row.full_cast = d["cast"] or None

backend/app/plex/sync.py

@@ -17,7 +17,7 @@ from sqlalchemy.orm import Session
 
 from app import sysconfig
 from app.models import PlexCollection, PlexItem, PlexLibrary, PlexSeason, PlexShow
-from app.plex import people
+from app.plex import detail, people
 from app.plex.client import PlexClient, PlexError, PlexNotConfigured
 from app.plex.lookups import by_rating_key
 
@@ -258,6 +258,7 @@ def _enrich_people_batch(db: Session, plex: PlexClient, limit: int = _ENRICH_BAT
             log.debug("Plex people enrich fetch failed for %s: %s", row.rating_key, e)
             continue  # leave people_enriched_at NULL so it's retried on a later run
         people.enrich_row_people(db, row, people.cast_from_meta(meta))
+        detail.apply_rich_detail(row, meta)  # imdb/tagline/full_cast → served from the row, not live
         row.people_enriched_at = now
         n += 1
     db.commit()