feat(icons): Orbit app icon + template tray icon across all clients

New brand icon (Orbit — a node circling a block-cursor core, amber-gold on
warm-dark, matching the desktop theme):
- iOS: Assets.xcassets/AppIcon.appiconset (opaque 1024, was no icon)
- desktop: resources/icon.png (rounded 1024 → .icns at package time)
- desktop tray: trayTemplate.png/@2x — a proper macOS TEMPLATE (black shapes on
  transparent, system-tinted) replacing the old white blob
- web: public/icon.svg (vector favicon/PWA)
Master SVGs rendered with rsvg-convert.

ios/App/WebTerm/Resources/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -0,0 +1,6 @@
+{
+  "images" : [
+    { "filename" : "AppIcon-1024.png", "idiom" : "universal", "platform" : "ios", "size" : "1024x1024" }
+  ],
+  "info" : { "author" : "xcode", "version" : 1 }
+}