fix(icons): apply file path substitutions in launcher icon resolution (#1877)

Follow-up to #1867. The launcher's AppIconRenderer used its own
Quickshell.iconPath() call without going through appIdSubstitutions,
so PWA icons configured via regex file path rules were not resolved
in the app launcher.

Co-authored-by: odtgit <[email protected]>

quickshell/Widgets/AppIconRenderer.qml

@@ -49,6 +49,14 @@ Item {
     readonly property string iconPath: {
         if (hasSpecialPrefix || !iconValue)
             return "";
+        const moddedId = Paths.moddedAppId(iconValue);
+        if (moddedId !== iconValue) {
+            if (moddedId.startsWith("~") || moddedId.startsWith("/"))
+                return Paths.toFileUrl(Paths.expandTilde(moddedId));
+            if (moddedId.startsWith("file://"))
+                return moddedId;
+            return Quickshell.iconPath(moddedId, true);
+        }
         return Quickshell.iconPath(iconValue, true) || DesktopService.resolveIconPath(iconValue);
     }