Add branded Finder icon for Probo Agent.app

The macOS URL-handler bundle had no CFBundleIconFile, so
Finder showed the generic app icon after PKG install. Keep a
single master PNG and generate AppIcon.icns at build time
with sips/iconutil, matching the auditor-mode approach.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

cmd/probo-agent/installer/macos/enroll-ui/.gitignore

@@ -4,3 +4,9 @@
 
 # Rendered by build.sh from *.tmpl (do not commit)
 Shared/*.generated.swift
+
+# Generated from Resources/icon-original.png (build staging preferred;
+# ignore if produced locally under enroll-ui).
+Resources/AppIcon.icns
+Resources/AppIcon.iconset/
+Resources/icon-padded.png

cmd/probo-agent/installer/macos/enroll-ui/Info.plist.tmpl

@@ -21,6 +21,8 @@
     <string>Probo Agent</string>
     <key>CFBundleDisplayName</key>
     <string>Probo Agent</string>
+    <key>CFBundleIconFile</key>
+    <string>AppIcon</string>
     <key>CFBundlePackageType</key>
     <string>APPL</string>
     <key>CFBundleShortVersionString</key>