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/main.ts

@@ -0,0 +1,9 @@
+import { mount } from 'svelte'
+import './app.css'
+import App from './App.svelte'
+
+const app = mount(App, {
+  target: document.getElementById('app')!,
+})
+
+export default app