feat(filters): pick one year from a decade grid, in the feed and in Plex

A shared YearPicker: the recent years as chips with their counts, and a
More dialog that lays every year out by decade (sortable by count), so a
ninety-year library fits on one screen. The feed's scrolling popover gives
way to it; the Plex rail gets it above its range fields, a pick setting
both ends. The Plex facets now count titles per year, the year filter left
out.

backend/app/plex/library.py

@@ -242,6 +242,7 @@ def facets(db: Session, user: User, *, scope: str, show: str, lang: str, f: Libr
         "content_ratings": [],
         "studios": [],
         "playable": [],
+        "years": [],
         "year_min": None,
         "year_max": None,
         "rating_max": None,
@@ -302,7 +303,7 @@ def facets(db: Session, user: User, *, scope: str, show: str, lang: str, f: Libr
     cr_counts: dict[str, int] = {}
     studio_counts: dict[str, int] = {}
     playable_counts: dict[str, int] = {}
-    years: list[int] = []
+    year_counts: dict[int, int] = {}
     ratings: list[float] = []
     durs: list[int] = []
 
@@ -383,21 +384,22 @@ def facets(db: Session, user: User, *, scope: str, show: str, lang: str, f: Libr
             )
             for cls, c in db.execute(pcq).all():
                 playable_counts[cls] = playable_counts.get(cls, 0) + c
-        # Year bounds — exclude the year filter.
-        by = db.execute(
+        # Titles per year — exclude the year filter, so a picked year never empties the list it was
+        # picked from. The year bounds are read from the same counts.
+        yq = (
             wsq(
-                select(func.min(model.year), func.max(model.year)),
+                select(model.year, func.count()),
                 model,
                 ids,
                 {**p, "year_min": None, "year_max": None},
                 kind_movie,
                 True,
             )
-        ).one()
-        if by[0] is not None:
-            years.append(by[0])
-        if by[1] is not None:
-            years.append(by[1])
+            .where(model.year.isnot(None))
+            .group_by(model.year)
+        )
+        for y, c in db.execute(yq).all():
+            year_counts[y] = year_counts.get(y, 0) + c
         # Rating max — exclude the rating filter. Coalesce(imdb, audience) to match the score the
         # rating filter and the UI badge use (IMDb preferred, audience fallback).
         br = db.scalar(
@@ -465,8 +467,9 @@ def facets(db: Session, user: User, *, scope: str, show: str, lang: str, f: Libr
             for c in PLAYBACK_CLASSES
             if c in playable_counts
         ],
-        "year_min": min(years) if years else None,
-        "year_max": max(years) if years else None,
+        "years": [{"year": y, "count": c} for y, c in sorted(year_counts.items(), reverse=True)],
+        "year_min": min(year_counts) if year_counts else None,
+        "year_max": max(year_counts) if year_counts else None,
         "rating_max": max(ratings) if ratings else None,
         "duration_min": min(durs) if durs else None,
         "duration_max": max(durs) if durs else None,