refactor(plex): the browse, detail, people and collection pages read through queries and write through the service

The HTTP files browse, detail, people, collections and _shared do no database work of their own
now. New plex/queries.py (the rows a page shows, a user's watch state through userscope),
plex/service.py (the info pages' enrichment, a collection's editable flag, the row kept after a
failed follow-up read, the person bio's background fetch; none commits), plex/library.py (the
unified browse feed, its search and facets) and plex/collections.py (a collection's source,
editability, card, certificate and member order). Every watch-state join in the moved code names
its owner through owned_by.

Pins 354 -> 178 in 4 files; basedpyright baseline 132 -> 118.

backend/app/plex/detail.py

@@ -1,10 +1,11 @@
 """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.
 
-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`)."""
+Shared by the live info-page path (`plex.service.enrich_movie` / `enrich_show`) 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
 from app.plex.plaintext import plain_text