Replace QML CAVA polling with SSE server for smooth bars

DataSource fork+exec was limited to ~1fps. Now cava pipes into a Python
SSE server (port 5555) and the HTML connects directly via EventSource,
getting updates at up to 60fps without QML overhead.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugin/contents/ui/main.qml

@@ -16,6 +16,7 @@ WallpaperItem {
         settings {
             javascriptEnabled: true
             localContentCanAccessFileUrls: true
+            localContentCanAccessRemoteUrls: true
             localStorageEnabled: false
         }
 
@@ -51,18 +52,4 @@ WallpaperItem {
         }
     }
 
-    // Polls CAVA bars at ~60fps
-    Plasma5Support.DataSource {
-        id: cavaSource
-        engine: "executable"
-        connectedSources: ["cat /tmp/skeledance_bars 2>/dev/null || echo ''"]
-        interval: 80
-
-        onNewData: function(sourceName, data) {
-            var raw = data["stdout"].trim()
-            if (raw !== "") {
-                webView.runJavaScript("updateBars(" + JSON.stringify(raw) + ")")
-            }
-        }
-    }
 }