chore(plex): dedup frontend formatters + LS key, drop dead wasPlaying pref

- format.ts: new formatRuntime() ("1h 30m"); PlexBrowse dur() + PlexInfo
  fmtDur() were byte-identical copies, now both call it.
- PlexPlayer fmt() delegates to formatDuration (keeps the NaN/negative clamp
  the live media clock needs); local reimplementation gone.
- Register LS.plexPlayerPrefs; PlexPlayer uses it instead of a bare string.
- Remove the dead PlexPlayerPrefs.wasPlaying field (written on play/pause, never
  read) + its two patchPrefs writes.
- PlexBrowse item page: drop the redundant onStateChange={() => q.refetch()} —
  PlexInfo.setState already invalidates ["plex-item", id], so q refetches itself.

frontend/src/components/PlexPlayer.tsx

@@ -33,7 +33,8 @@ import {
   X,
 } from "lucide-react";
 import { api, type PlexMarker } from "../lib/api";
-import { useAccountPersistedObject } from "../lib/storage";
+import { formatDuration } from "../lib/format";
+import { LS, useAccountPersistedObject } from "../lib/storage";
 import { useDismiss } from "../lib/useDismiss";
 import { useBackToClose } from "../lib/history";
 
@@ -63,7 +64,6 @@ function subOrdForLang(subs: SubStream[], lang: string): number | null {
 type PlexPlayerPrefs = {
   volume: number; // 0..1
   muted: boolean;
-  wasPlaying: boolean; // resume-playing intent across reloads (best-effort; browsers may block autoplay)
   audioLang: string; // "" = default first audio
   subLang: string; // "" = subtitles off
   subOffset: number; // seconds, +later / -earlier (client-side cue shift)
@@ -90,7 +90,6 @@ type PlexPlayerPrefs = {
 const DEFAULT_PREFS: PlexPlayerPrefs = {
   volume: 1,
   muted: false,
-  wasPlaying: true,
   audioLang: "",
   subLang: "",
   subOffset: 0,
@@ -165,13 +164,10 @@ const HLS_SUB_LAG = 1.0;
 // the queue instead of the item's own episode neighbours.
 type Props = { itemId: string; onClose: () => void; queue?: string[] };
 
+// Seekbar clock — same H:MM:SS / M:SS shape as the shared formatDuration, but the live media clock
+// can be NaN/negative before metadata loads, so clamp to 0 first (formatDuration never sees null here).
 function fmt(t: number): string {
-  if (!isFinite(t) || t < 0) t = 0;
-  const s = Math.floor(t % 60);
-  const m = Math.floor((t / 60) % 60);
-  const h = Math.floor(t / 3600);
-  const pad = (n: number) => String(n).padStart(2, "0");
-  return h ? `${h}:${pad(m)}:${pad(s)}` : `${m}:${pad(s)}`;
+  return formatDuration(isFinite(t) && t >= 0 ? t : 0);
 }
 
 export default function PlexPlayer({ itemId, onClose, queue }: Props) {
@@ -217,7 +213,7 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
 
   // Per-account persisted player prefs — survive F5, carry across items.
   const [prefs, patchPrefs] = useAccountPersistedObject<PlexPlayerPrefs>(
-    "siftlode.plexPlayerPrefs",
+    LS.plexPlayerPrefs,
     DEFAULT_PREFS,
   );
   const { volume, muted } = prefs;
@@ -419,18 +415,12 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
         /* ignore */
       }
     };
-    const onPlay = () => {
-      setPlaying(true);
-      patchPrefs({ wasPlaying: true }); // remember play intent for F5 (best-effort; autoplay may be blocked)
-    };
-    const onPause = () => {
-      setPlaying(false);
-      patchPrefs({ wasPlaying: false });
-    };
+    const onPlay = () => setPlaying(true);
+    const onPause = () => setPlaying(false);
     // A seek that restarts the hls.js session detaches/re-attaches the media, firing 'emptied' —
     // which silently flips paused=true WITHOUT a 'pause' event, so the play/pause pair alone let the
     // button lie (⏸ shown while actually paused). Resync the flag from reality on the settling events
-    // so the icon can never contradict the video. (Does not touch the wasPlaying pref.)
+    // so the icon can never contradict the video.
     const syncPlaying = () => setPlaying(!video.paused);
     video.addEventListener("timeupdate", onTime);
     video.addEventListener("play", onPlay);