feat(player): webview audio backend for platforms without a native one

Adds WebviewAudioBackend, used on non-Linux/non-Android targets (e.g.
Windows) where there is no libmpv/ExoPlayer. Instead of decoding, it
emits a WebviewAudioLoad event with the stream URL; a frontend <audio>
element (WebviewAudioAdapter + webviewAudio service) plays it and reports
state/position back through the existing player_report_* round-trip, so
the Rust PlayerController stays the single source of truth. Play/pause/
seek reach the element via the existing ControlCommand event.

All video already renders in the webview on every platform, so this
completes audio-only playback for Windows (video via WebView2, audio via
<audio>). Pure Rust + Tauri events, so it still cross-compiles from Linux.

Regenerates bindings.ts (adds webview_audio_load; also carries the
equalizer EQ bindings).

TRACES: UR-003, UR-004, UR-005 | DR-004

src-tauri/src/player/events.rs

@@ -156,6 +156,25 @@ pub enum PlayerStatusEvent {
         /// Target position in seconds (only meaningful for "seek").
         position: Option<f64>,
     },
+    /// Ask the frontend webview `<audio>` element to load and play a stream.
+    ///
+    /// Emitted by `WebviewAudioBackend` on platforms with no native audio
+    /// backend (e.g. Windows): audio-only playback is rendered by an `<audio>`
+    /// element in the webview, mirroring how all video already renders through
+    /// the webview `<video>`. The element then reports its state/position back
+    /// through the `player_report_*` commands, so the Rust controller stays the
+    /// single source of truth. Subsequent play/pause/seek/stop reach the element
+    /// via `ControlCommand`.
+    WebviewAudioLoad {
+        /// Stream URL for the `<audio>` element to play.
+        url: String,
+        /// Jellyfin item id, used as the media_id when reporting state back.
+        media_id: Option<String>,
+        /// Resume position in seconds (0 = start from the beginning).
+        position: f64,
+        /// Whether to begin playing immediately after loading.
+        autoplay: bool,
+    },
 }
 
 /// Trait for emitting player events to the frontend.