Refactor desktop app into separate client and proxy apps

apps/yaak-proxy/main.tsx

@@ -0,0 +1,77 @@
+import "./main.css";
+import { invoke } from "@tauri-apps/api/core";
+import { StrictMode } from "react";
+import { useState } from "react";
+import { createRoot } from "react-dom/client";
+
+type ProxyStartResult = {
+  port: number;
+  alreadyRunning: boolean;
+};
+
+function App() {
+  const [status, setStatus] = useState("Idle");
+  const [port, setPort] = useState<number | null>(null);
+  const [busy, setBusy] = useState(false);
+
+  async function startProxy() {
+    setBusy(true);
+    setStatus("Starting...");
+    try {
+      const result = await invoke<ProxyStartResult>("proxy_start", {
+        port: 9090,
+      });
+      setPort(result.port);
+      setStatus(result.alreadyRunning ? "Already running" : "Running");
+    } catch (err) {
+      setStatus(`Failed: ${String(err)}`);
+    } finally {
+      setBusy(false);
+    }
+  }
+
+  async function stopProxy() {
+    setBusy(true);
+    setStatus("Stopping...");
+    try {
+      const stopped = await invoke<boolean>("proxy_stop");
+      setPort(null);
+      setStatus(stopped ? "Stopped" : "Not running");
+    } catch (err) {
+      setStatus(`Failed: ${String(err)}`);
+    } finally {
+      setBusy(false);
+    }
+  }
+
+  return (
+    <main className="app-shell">
+      <section className="hero-card">
+        <p className="eyebrow">Monorepo Smoke Test</p>
+        <h1>Yaak Proxy</h1>
+        <p className="lede">
+          This is a minimal proxy app stub running on the new `apps/yaak-proxy`
+          and `crates-tauri/yaak-app-proxy` structure.
+        </p>
+        <div className="controls">
+          <button className="btn" disabled={busy} onClick={startProxy}>
+            Start Proxy
+          </button>
+          <button className="btn ghost" disabled={busy} onClick={stopProxy}>
+            Stop Proxy
+          </button>
+        </div>
+        <div className="status">
+          <span>Status: {status}</span>
+          {port != null ? <span>Port: {port}</span> : null}
+        </div>
+      </section>
+    </main>
+  );
+}
+
+createRoot(document.getElementById("root") as HTMLElement).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+);