Initial bass-manage Qt Quick / Kirigami control panel.

PipeWire LFE/center mix UI with live pw-cli controls and conf save/reload.

icons/sliders-horizontal.svg

@@ -0,0 +1,21 @@
+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <path d="M10 5H3" />
+  <path d="M12 19H3" />
+  <path d="M14 3v4" />
+  <path d="M16 17v4" />
+  <path d="M21 12h-9" />
+  <path d="M21 19h-5" />
+  <path d="M21 5h-7" />
+  <path d="M8 10v4" />
+  <path d="M8 12H3" />
+</svg>