Add macOS target and put platform in artifact names

Adds a mac zip target (x64 + arm64) so releases cover all three
platforms. Builds unsigned: electron-builder skips code signing when not
running on macOS, so these need the quarantine attribute cleared.

Also puts ${os} in artifactName. Without it the Windows and macOS zips
were both WhatsThatMusic-1.0.0-x64.zip, which collide as release assets
and give no clue which platform they are.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

desktop-client/package.json

@@ -16,7 +16,10 @@
       "!tests/**"
     ],
     "extraResources": [
-      { "from": "../overlay", "to": "overlay" }
+      {
+        "from": "../overlay",
+        "to": "overlay"
+      }
     ],
     "extraMetadata": {
       "main": "index.js"
@@ -28,13 +31,22 @@
       "certificateSubjectName": null
     },
     "linux": {
-      "target": ["AppImage"],
+      "target": [
+        "AppImage"
+      ],
       "icon": "build/icon.png",
       "category": "AudioVideo",
       "synopsis": "YouTube Music player with a now-playing overlay for OBS",
       "maintainer": "What's That Music"
     },
-    "artifactName": "${productName}-${version}-${arch}.${ext}"
+    "artifactName": "${productName}-${version}-${os}-${arch}.${ext}",
+    "mac": {
+      "target": [
+        "zip"
+      ],
+      "icon": "build/icon.png",
+      "category": "public.app-category.music"
+    }
   },
   "dependencies": {
     "express": "^5.2.1",