feat: add cava audio visualizer component

Cava.qml

@@ -0,0 +1,26 @@
+pragma Singleton
+
+import QtQuick
+import Quickshell
+import Quickshell.Io
+
+Singleton {
+  id: root
+
+  readonly property string configPath: {
+    const url = Quickshell.shellPath("assets/cava.conf").toString();
+    return url.startsWith("file://") ? decodeURIComponent(url.substring(7)) : url;
+  }
+  property var values: []
+
+  Process {
+    running: true
+    command: ["cava", "-p", root.configPath]
+
+    stdout: SplitParser {
+      onRead: line => {
+        root.values = line.split(";").map(Number).filter(v => !Number.isNaN(v));
+      }
+    }
+  }
+}