macos: run as LSUIElement menubar app with NSStatusItem

Ship Lan Mouse on macOS as an accessory app (no Dock icon, no main
window on launch) with a status-bar item for show/quit. Closing the
window hides it instead of quitting so the menu bar stays the primary
surface.

- build-aux/macos-lsui-element.plist: LSUIElement=true plus
  NSInputMonitoringUsageDescription and NSAppleEventsUsageDescription
  (merged into Info.plist via cargo-bundle's osx_info_plist_exts).
- lan-mouse-gtk/src/macos_status_item.rs: NSStatusItem setup via raw
  objc_msgSend FFI. Loads a bundled 22pt PNG as a template image so
  it auto-tints for light/dark menu bars.
- scripts/makeicns.sh: emit Contents/Resources/menubar-template.png
  from the existing SVG.
- scripts/copy-macos-dylib.sh: flatten cargo-bundle's preserved
  target/ subdir under Resources so NSBundle pathForResource: finds
  the template image.
- lan-mouse-gtk/src/lib.rs: register the new modules, set up a
  Cmd+Q-wired quit action, configure bundle env vars (schemas,
  XDG_DATA_DIRS, GTK_DATA_PREFIX) when running from inside the .app,
  and filter the known upstream Gtk theme-parser warning spam.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/makeicns.sh

@@ -67,12 +67,13 @@ magick -size ${CANVAS}x${CANVAS} xc:none \
 # 3) Composite the artwork onto the background, centered inside the content area.
 magick "$workdir/background.png" \
     "$workdir/content.png" -geometry +${CONTENT_OFFSET}+${CONTENT_OFFSET} -composite \
-    "$workdir/icon-1024.png"
+    -colorspace sRGB -type TrueColorAlpha PNG32:"$workdir/icon-1024.png"
 
 # 4) Generate each iconset size from the master so all sizes share the same
 #    squircle proportions and look consistent at every resolution.
 for size in 1024 512 256 128 64 32 16; do
-    magick "$workdir/icon-1024.png" -resize ${size}x${size} "$workdir/${size}.png"
+    magick "$workdir/icon-1024.png" -resize ${size}x${size} \
+        -colorspace sRGB -type TrueColorAlpha PNG32:"$workdir/${size}.png"
 done
 
 cp "$workdir/1024.png" "$iconset"/icon_512x512@2x.png
@@ -86,4 +87,51 @@ cp "$workdir/32.png"   "$iconset"/icon_32x32.png
 cp "$workdir/32.png"   "$iconset"/icon_16x16@2x.png
 cp "$workdir/16.png"   "$iconset"/icon_16x16.png
 
-iconutil -c icns "$iconset" -o "$icns"
+mkdir -p "$(dirname "$icns")"
+
+# Menu bar template icon: flatten all RGB channels to 0 (black) while keeping
+# alpha so the artwork reads as a clean silhouette. NSStatusBarButton tints
+# template images to match the menu bar appearance in light and dark modes.
+menubar_template="$(dirname "$icns")/menubar-template.png"
+rsvg-convert -w 44 -h 44 "$svg" -o "$workdir/menubar-44.png"
+magick "$workdir/menubar-44.png" -channel RGB -evaluate set 0 +channel \
+    "$menubar_template"
+
+if ! iconutil -c icns "$iconset" -o "$icns"; then
+    if ! command -v perl >/dev/null 2>&1; then
+        echo "iconutil failed and perl is not available for the fallback icns writer" >&2
+        exit 1
+    fi
+
+    echo "iconutil rejected the iconset; writing icns directly" >&2
+    perl - "$icns" "$iconset" <<'PERL'
+use strict;
+use warnings;
+
+my ($icns, $iconset) = @ARGV;
+my @icons = (
+    [ 'icp4', "$iconset/icon_16x16.png" ],
+    [ 'ic11', "$iconset/icon_16x16\@2x.png" ],
+    [ 'icp5', "$iconset/icon_32x32.png" ],
+    [ 'ic12', "$iconset/icon_32x32\@2x.png" ],
+    [ 'ic07', "$iconset/icon_128x128.png" ],
+    [ 'ic13', "$iconset/icon_128x128\@2x.png" ],
+    [ 'ic08', "$iconset/icon_256x256.png" ],
+    [ 'ic14', "$iconset/icon_256x256\@2x.png" ],
+    [ 'ic09', "$iconset/icon_512x512.png" ],
+    [ 'ic10', "$iconset/icon_512x512\@2x.png" ],
+);
+
+my $body = '';
+for my $icon (@icons) {
+    my ($type, $path) = @$icon;
+    open my $fh, '<:raw', $path or die "$path: $!";
+    local $/;
+    my $png = <$fh>;
+    $body .= $type . pack('N', length($png) + 8) . $png;
+}
+
+open my $out, '>:raw', $icns or die "$icns: $!";
+print {$out} 'icns' . pack('N', length($body) + 8) . $body;
+PERL
+fi