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/collections.py

@@ -0,0 +1,122 @@
+"""What a collection is to the app: where it comes from, whether it may be edited, its card, its
+effective content rating, and how its members order — shared by the collection pages, the info
+page's collection strips and the admin editor."""
+
+from collections.abc import Callable
+from datetime import date, datetime
+from typing import Any, NamedTuple
+
+from app.plex.models import PlexCollection
+
+# The most-restrictive → least ordering used to pick a collection's effective content rating from its
+# members (Plex shows one cert on the collection; we don't store it, so derive it).
+_CERT_RANK = {
+    "G": 1,
+    "TV-Y": 1,
+    "TV-Y7": 1,
+    "TV-G": 1,
+    "PG": 2,
+    "TV-PG": 2,
+    "PG-13": 3,
+    "TV-14": 3,
+    "R": 4,
+    "TV-MA": 4,
+    "NC-17": 5,
+}
+
+
+def collection_cert(certs: list[str | None]) -> str | None:
+    ranked = [(c, _CERT_RANK.get(c, 0)) for c in certs if c]
+    return max(ranked, key=lambda x: x[1])[0] if ranked else None
+
+
+_STRIP_PROVIDERS = ("imdb", "tmdb", "tvdb", "trakt")
+
+
+def collection_source(col: PlexCollection) -> str:
+    first = (col.title or "").strip().split(" ", 1)[0].lower()
+    if first in _STRIP_PROVIDERS:
+        return first
+    if col.smart:
+        return "smart"
+    return "collection"
+
+
+def collection_editable(c: PlexCollection) -> bool:
+    """Effective editability: the admin marked it editable AND it's a plain manual collection — never
+    smart, never an external auto-list (IMDb/TMDb/…), which are managed outside Plex."""
+    return bool(c.editable) and not c.smart and collection_source(c) == "collection"
+
+
+def collection_card(c: PlexCollection) -> dict:
+    return {
+        "id": c.rating_key,
+        "title": c.title,
+        "summary": c.summary,
+        "thumb": f"/api/plex/image/{c.rating_key}" if c.thumb_key else None,
+        "child_count": c.child_count,
+        "smart": c.smart,
+        "source": collection_source(c),
+        "editable": c.editable,
+        "can_edit": collection_editable(
+            c
+        ),  # whether the edit controls should be offered (admin UI)
+    }
+
+
+class Member(NamedTuple):
+    """One collection member flattened to everything the Sort control can order by. The page's two
+    legs are different tables (movies and shows), so there is no single query to ORDER BY — the
+    ordering is a pure list sort over these, which is also what makes it unit-testable."""
+
+    kind: str  # "movie" | "show"
+    obj: Any  # PlexItem | PlexShow, carried through to the card serializer
+    title: str  # lower-cased; never NULL (the column is not nullable)
+    year: int | None
+    rating: float | None
+    added: datetime | None
+    release: date | None
+    duration: int | None  # movies only — a show has no single runtime
+    last_watched: datetime | None
+
+
+# Sort key -> what to read off a Member. Pinned to `PLEX_SORT_KEYS` by a test: the collection page
+# shows the SAME Sort control as the browse grid, so a key this map is missing would be an option
+# that silently does nothing here.
+MEMBER_SORT_KEYS: dict[str, Callable[[Member], Any]] = {
+    "added": lambda m: m.added,
+    "lastwatched": lambda m: m.last_watched,
+    "release": lambda m: m.release,
+    "year": lambda m: m.year,
+    "rating": lambda m: m.rating,
+    "duration": lambda m: m.duration,
+    "title": lambda m: m.title,
+}
+
+# What the page ordered by before it had a control, and still its default: a film series wants to be
+# read in release order, not by whenever Plex happened to ingest it.
+DEFAULT_MEMBER_SORT = "year"
+
+
+def sort_members(
+    members: list[Member], sort: str, sort_dir: str, alpha: dict[str, int] | None = None
+) -> list[Member]:
+    """Order a collection's members by one of `PLEX_SORT_KEYS`.
+
+    Two properties worth stating because they are easy to get wrong with a plain `reverse=True`:
+    members with no value for the key sink to the END in BOTH directions (matching the browse grid's
+    `nullslast()` — a movie with no rating is not "the worst rated"), and ties always resolve
+    title-ascending, so flipping the direction reverses the ranking rather than the alphabet inside
+    it. An unknown key falls back to the page's default instead of returning an arbitrary order.
+
+    `alpha` ranks each title in the reader's alphabet (`collation.sorted_words`); without it, titles
+    compare as Python strings, which puts every accented initial after "z"."""
+    by_title = (lambda m: alpha[m.title]) if alpha is not None else (lambda m: m.title)
+    key = MEMBER_SORT_KEYS.get(sort, MEMBER_SORT_KEYS[DEFAULT_MEMBER_SORT])
+    if key is MEMBER_SORT_KEYS["title"]:
+        key = by_title
+    ordered = sorted(members, key=by_title)  # stable secondary, applied first
+    have = [m for m in ordered if key(m) is not None]
+    missing = [m for m in ordered if key(m) is None]
+    have.sort(key=key, reverse=sort_dir != "asc")
+    return have + missing