charles: fix desktop icons and mime integration

This addresses icon and mimetype issues for different versions:

- For Charles 5+:
  - Update desktop entry to use 'charles-proxy5'.
  - Install the upstream provided shared-mime-info XML. This correctly
    maps mime types to the upstream icon names (e.g. charles-proxy5-har).
- For Charles 4: Install the upstream provided shared-mime-info XML.
- For Charles 3: Fix icon installation paths (upstream tarball has
  non-standard layout). No mime icons are available for this version.

pkgs/applications/networking/charles/default.nix

@@ -31,7 +31,7 @@ let
         desktopName = "Charles";
         exec = "charles %F";
         genericName = "Web Debugging Proxy";
-        icon = "charles-proxy";
+        icon = "charles-proxy" + lib.optionalString (lib.versionAtLeast version "5.0") "5";
         mimeTypes = [
           "application/x-charles-savedsession"
           "application/x-charles-savedsession+xml"
@@ -73,8 +73,24 @@ let
         mkdir -p $out/share/applications
         ln -s ${desktopItem}/share/applications/* $out/share/applications/
 
-        mkdir -p $out/share/icons
-        cp -r icon $out/share/icons/hicolor
+        ${
+          if lib.versionOlder version "4.0" then
+            ''
+              for size in 16 32 48 64 128 256 512; do
+                install -Dm644 icon/charles_icon$size.png $out/share/icons/hicolor/''${size}x''${size}/apps/charles-proxy.png
+              done
+              install -Dm644 icon/charles_icon.svg $out/share/icons/hicolor/scalable/apps/charles-proxy.svg
+            ''
+          else
+            ''
+              mkdir -p $out/share/icons
+              cp -r icon $out/share/icons/hicolor
+              if [ -d "etc/mime" ]; then
+                mkdir -p $out/share/mime/packages
+                cp etc/mime/*.xml $out/share/mime/packages/
+              fi
+            ''
+        }
 
         runHook postInstall
       '';