Initial commit: pwweb - PipeWire WebUI

C++ backend with SSE streaming (reuses qpwgraph PipeWire callbacks).
Svelte frontend with custom SVG canvas for port-level connections.

Features:
- Live PipeWire graph via SSE
- Drag output->input port to connect
- Double-click or select+Delete to disconnect
- Node positions saved to localStorage
- Pan (drag bg) and zoom (scroll)
- Port type coloring (audio=green, midi=red, video=blue)

frontend/src/App.svelte

@@ -0,0 +1,14 @@
+<script lang="ts">
+  import GraphCanvas from './components/GraphCanvas.svelte';
+</script>
+
+<GraphCanvas />
+
+<style>
+  :global(body) {
+    margin: 0;
+    padding: 0;
+    overflow: hidden;
+    background: #14141e;
+  }
+</style>