feat(call): native WASAPI system-audio for screen-share (Windows)

Hooks the custom screen-share picker up to a native WASAPI loopback
capture so "Mit System-Sound" no longer falls back to the OS picker on
Windows. Rust side opens the default render endpoint, channels 48 kHz
f32 stereo to an AudioWorklet, which feeds a MediaStreamDestination for
LiveKit to publish as ScreenShareAudio. Ring buffer sized for latency
(80 ms target, drop-to-target on overflow) and the AudioContext is
resumed eagerly so initial burstiness can't pile up.

Adds a temporary attachTrack:audio diagnostic log to confirm source
tagging matches between old and new clients.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop/src-tauri/Cargo.lock

@@ -852,6 +852,7 @@ dependencies = [
  "tauri-plugin-updater",
  "tauri-plugin-window-state",
  "tokio",
+ "wasapi",
  "windows 0.58.0",
  "xcap",
 ]
@@ -8125,6 +8126,19 @@ dependencies = [
  "try-lock",
 ]
 
+[[package]]
+name = "wasapi"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f6b03b82e419f186fcdc06ac6068621bdadc88b89b2612067f1c021ad2c9449"
+dependencies = [
+ "log",
+ "num-integer",
+ "widestring",
+ "windows 0.57.0",
+ "windows-core 0.57.0",
+]
+
 [[package]]
 name = "wasi"
 version = "0.9.0+wasi-snapshot-preview1"
@@ -8431,6 +8445,12 @@ dependencies = [
  "wasite",
 ]
 
+[[package]]
+name = "widestring"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72069c3113ab32ab29e5584db3c6ec55d416895e60715417b5b883a357c3e471"
+
 [[package]]
 name = "winapi"
 version = "0.3.9"