fix(audio-player): playback speed silently reverted to 1x on every reload

restorePosition() swaps the <audio> element's src (manifest track for
multi-file books, whole file for single-file, plain URL on offline
start), and loading new media resets playbackRate to the element
default. init() had applied the persisted speed before any src
existed, so after the swap every load actually played at 1x while the
Speed pill still showed the stored value — pick 1.5x, reload, and
audio was back at 1x.

The seekTo() src-swap path already re-applied the rate; the initial
load paths now do the same (manifest branch + offline-catch branch).
Surfaced by the phase-1 speed-list browser check: button label and
audio.playbackRate disagreed after reload.

web/src/audio.ts

@@ -323,6 +323,11 @@ Alpine.data("audioReader", () => ({
         const audio = this.audio();
         if (audio && !audio.getAttribute("src") && this.tracks[0]) {
           audio.setAttribute("src", this.tracks[0].url);
+          // Setting src resets playbackRate to the element default —
+          // re-apply, mirroring the seekTo() src-swap path. Without this
+          // the pill said 1.5× while audio actually played at 1× after
+          // every reload (surfaced by the speed-list browser check).
+          audio.playbackRate = this.speed;
         }
       }
       if (progress.ok) {
@@ -351,6 +356,7 @@ Alpine.data("audioReader", () => ({
       if (audio && !audio.getAttribute("src") && this.fileUrl) {
         this.tracks = [{ url: this.fileUrl, start: 0, end: 0 }];
         audio.setAttribute("src", this.fileUrl);
+        audio.playbackRate = this.speed;
       }
     }
   },