feat(plex): filter the feed by playback class (Direct Play / Direct Stream / Transcode HW/SW)

Adds a movie-scoped "Playback" filter to the Plex feed so a user can isolate items by how
they play — the groundwork for collecting HW-transcodable (or no-transcode) versions.

Four classes derived from the stored `playable` + a new `transcode_hw` facet:
- Direct Play (direct), Direct Stream (remux)
- Transcode · HW  — playable=transcode AND the iGPU can hardware-transcode it
- Transcode · SW  — playable=transcode, software libx264 only

The HW/SW split is precise, not codec-only: a 10-bit/HDR HEVC is HW-decodable yet breaks the
VAAPI nv12 pipeline (the same case plex/stream special-cases), so it must count as SW.

Backend:
- New PlexItem columns (migration 0077): transcode_hw, video_bit_depth, media_probed_at.
  Migration backfills transcode_hw codec-only so the filter works immediately.
- `plex.sync.transcode_hw_capable` is the single classifier; the HW-decodable codec set moves
  to sync as `HW_DECODABLE_CODECS` and plex.stream imports it, so the catalog facet and the
  runtime encoder choice can't disagree by codec.
- Bit-depth backfill (`_probe_media_batch`, wired into sync): probes only HW-decodable transcode
  items' video Stream for bit-depth + HDR and refines a 10-bit/HDR HEVC to software. Bounded
  per run, watermarked by media_probed_at. A codec change resets the watermark (stale probe).
- Filter + self-excluded facet on a shared `playback_class_expr` CASE (movie-leg only — a show
  is an aggregate with no single class). transcode_hw threaded onto the feed/detail/card JSON.

Frontend:
- Multi-select "Playback" Combobox in the sidebar (movie scope, facet-empty drop-out), active
  chips, 4-way corner-dot badge (green/blue/amber/red) + tooltip, and an info-page playback chip
  with a codec · bit-depth subtitle. New `bg-info` (blue) token, i18n HU/EN parity.
- Fix a regression where the card's playback dot lost its hover tooltip: the full-card reveal
  overlay swallowed the cursor; the dot now sits above it (z-20).

Gate: backend full lane + frontend typecheck/lint/knip/prettier/vitest all green. Browser-UAT'd
on localdev (filter narrows to the SW set, facet counts, badge colour + tooltip, info chip).

frontend/src/components/PlexInfo.tsx

@@ -19,6 +19,7 @@ import i18n from "../i18n";
 import { Carousel } from "./Carousel";
 import PlexCollectionEditor from "./PlexCollectionEditor";
 import PlexPlaylistAdd from "./PlexPlaylistAdd";
+import { PLAYABLE_TINT, playableClass } from "./plexCards";
 
 // The rich "media info" surface for a Plex item — poster/art, IMDb score + link, content rating,
 // genres, director, cast (with photos), summary. Reused in TWO places: a full-page view opened from
@@ -253,6 +254,33 @@ function CrewPanel({
   );
 }
 
+// The playback-class chip (dot + Plex-native label), with a muted codec · bit-depth subtitle when
+// known. Class + colour are derived through the SAME shared helper the browse-card corner dot uses,
+// so the two surfaces can't drift. `overlay` tints the label for the dark player background.
+function PlaybackChip({ detail, overlay }: { detail: PlexItemDetail; overlay: boolean }) {
+  const { t } = useTranslation();
+  if (!detail.playable) return null;
+  const cls = playableClass(detail.playable, detail.transcode_hw);
+  const sub = [
+    detail.codec_video ? detail.codec_video.toUpperCase() : null,
+    detail.video_bit_depth != null ? `${detail.video_bit_depth}-bit` : null,
+  ]
+    .filter(Boolean)
+    .join(" · ");
+  return (
+    <span
+      className={`inline-flex items-center gap-1.5 rounded-full px-2 py-0.5 text-xs ${
+        overlay ? "bg-white/10 text-white/90" : "bg-surface text-muted"
+      }`}
+      title={t(`plex.playable.${cls}`)}
+    >
+      <span className={`h-2 w-2 shrink-0 rounded-full ${PLAYABLE_TINT[cls] ?? "bg-gray-400"}`} />
+      <span className="font-medium">{t(`plex.filter.playableOpt.${cls}`)}</span>
+      {sub && <span className="opacity-70">{sub}</span>}
+    </span>
+  );
+}
+
 type Props = {
   detail: PlexItemDetail;
   variant: "page" | "overlay";
@@ -479,6 +507,7 @@ export default function PlexInfo({
                     {detail.studio}
                   </Filterable>
                 )}
+                <PlaybackChip detail={detail} overlay={overlay} />
               </div>
 
               {/* Multi-source ratings row (E5 S5): IMDb / TMDb / audience, whichever are present. */}