feat(plex): expanded metadata filters, clickable info page, image disk cache

Backend (migration 0045_plex_filter_meta): plex_items gains rating (audienceRating
~IMDb), content_rating, studio, originally_available_at, and GIN-indexed genres /
directors / cast_names — all mirrored from the cheap section listing (no per-item API
calls; they also seed a future watch-habit recommender). /browse gains genre / content-
rating / year / rating / duration / added-within / director / actor / studio filters
(@> containment, GIN) + sort by year|rating|duration|release; new /facets endpoint
returns available genres+ratings (with counts) and the year/rating/duration bounds. A
thin on-disk image cache (.plex-img-cache) serves posters/art/cast photos from local
disk after first fetch (~7-14x faster repeat loads).

Frontend: PlexSidebar grows the full filter set (facet-driven genre/age chips, rating
steps, year range inputs, duration buckets, added-within, active people/studio chips,
clear-all); filters persist per-account as one JSON blob. PlexInfo metadata (year,
genre, director, cast, studio, IMDb score) is clickable → sets the matching filter and
returns to the filtered grid (page variant only; the in-player overlay stays read-only
so a stray click can't stop playback). i18n en/hu/de.

backend/alembic/versions/0045_plex_filter_meta.py

@@ -0,0 +1,62 @@
+"""Plex filterable/orderable metadata
+
+Revision ID: 0045_plex_filter_meta
+Revises: 0044_plex_catalog
+Create Date: 2026-07-05
+
+Adds the metadata the expanded Plex filter sidebar filters + orders on, mirrored cheaply from the
+Plex section listing (no per-item API calls): rating (audienceRating ~ IMDb), content rating, studio,
+release date, and GIN-indexed genre / director / cast arrays. These also double as the content
+signals a future watch-habit recommender would use.
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy.dialects import postgresql
+
+revision: str = "0045_plex_filter_meta"
+down_revision: Union[str, None] = "0044_plex_catalog"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column("plex_items", sa.Column("rating", sa.Float(), nullable=True))
+    op.add_column("plex_items", sa.Column("content_rating", sa.String(length=16), nullable=True))
+    op.add_column("plex_items", sa.Column("studio", sa.String(length=255), nullable=True))
+    op.add_column("plex_items", sa.Column("originally_available_at", sa.Date(), nullable=True))
+    op.add_column("plex_items", sa.Column("genres", postgresql.JSONB(), nullable=True))
+    op.add_column("plex_items", sa.Column("directors", postgresql.JSONB(), nullable=True))
+    op.add_column("plex_items", sa.Column("cast_names", postgresql.JSONB(), nullable=True))
+
+    op.create_index("ix_plex_items_rating", "plex_items", ["rating"])
+    op.create_index("ix_plex_items_content_rating", "plex_items", ["content_rating"])
+    op.create_index("ix_plex_items_studio", "plex_items", ["studio"])
+    op.create_index("ix_plex_items_originally_available_at", "plex_items", ["originally_available_at"])
+    op.create_index("ix_plex_items_genres_gin", "plex_items", ["genres"], postgresql_using="gin")
+    op.create_index("ix_plex_items_directors_gin", "plex_items", ["directors"], postgresql_using="gin")
+    op.create_index("ix_plex_items_cast_gin", "plex_items", ["cast_names"], postgresql_using="gin")
+
+
+def downgrade() -> None:
+    for ix in (
+        "ix_plex_items_cast_gin",
+        "ix_plex_items_directors_gin",
+        "ix_plex_items_genres_gin",
+        "ix_plex_items_originally_available_at",
+        "ix_plex_items_studio",
+        "ix_plex_items_content_rating",
+        "ix_plex_items_rating",
+    ):
+        op.drop_index(ix, table_name="plex_items")
+    for col in (
+        "cast_names",
+        "directors",
+        "genres",
+        "originally_available_at",
+        "studio",
+        "content_rating",
+        "rating",
+    ):
+        op.drop_column("plex_items", col)