Migrated the macOS bundle manifest to GTK3 by switching the package reference to gtk+-3.0, updating the theme resource path to gtk-3.0, and changing the GTK translation domain from gtk20 to gtk30.

Updated bundled runtime config payload from GTK2-style gtkrc to GTK3 settings.ini in the bundle manifest, and added a new osx/settings.ini with Mac theme/key-theme defaults and image settings.

    Updated osx/launcher.sh to remove the GTK2-specific GTK2_RC_FILES usage, switch module file paths from gtk-2.0 to gtk-3.0, and add GTK3-appropriate GTK_THEME / GTK_KEY_THEME environment variables for macOS runtime behavior.

    Checked the osx/ packaging scripts/manifests for other hardcoded GTK2 identifiers and confirmed none remain in that packaging scope after the migration.

osx/zoitechat.bundle

@@ -8,7 +8,7 @@
 
     <run-install-name-tool/>
     <launcher-script>${project}/launcher.sh</launcher-script >
-    <gtk>gtk+-2.0</gtk>
+    <gtk>gtk+-3.0</gtk>
   </meta>
 
   <plist>${project}/Info.plist</plist>
@@ -47,18 +47,18 @@
     ${prefix}/lib/pango/${pkg:pango:pango_module_version}/modules/
   </binary>
   <data>
-    ${prefix}/share/themes/Mac/gtk-2.0-key/gtkrc
+    ${prefix}/share/themes/Mac/gtk-3.0/gtk-keys.css
   </data>
 
-  <translations name="gtk20">
+  <translations name="gtk30">
     ${prefix}/share/locale
   </translations>
   <translations name="zoitechat">
     ${prefix}/share/locale
   </translations>
 
-  <data dest="${bundle}/Contents/Resources/etc/${gtkdir}/gtkrc">
-    ${project}/gtkrc
+  <data dest="${bundle}/Contents/Resources/etc/${gtkdir}/settings.ini">
+    ${project}/settings.ini
   </data>
 
   <data dest="${bundle}/Contents/Resources">