feat: Windows stack (daemon, installer, GUI)

Components:
- ostp-daemon: Windows Service with Named Pipe IPC
- ostp-installer: Setup wizard with admin privileges
- ostp-gui: Tauri dark theme UI (450x600)

Features:
- Background service management (OspabGuard)
- IPC commands: CONNECT/DISCONNECT/STATUS
- Firewall rules auto-configuration
- Wintun driver placeholder (download from wintun.net)
- Real-time stats display (upload/download/ping)

Note: Requires wintun.dll download for full functionality

ostp-gui/ui/app.js

@@ -0,0 +1,117 @@
+const { invoke } = window.__TAURI__.core;
+
+let isConnected = false;
+
+// Initialize
+document.addEventListener('DOMContentLoaded', async () => {
+    await loadServers();
+    await updateStatus();
+    
+    // Update stats every 2 seconds when connected
+    setInterval(async () => {
+        if (isConnected) {
+            await updateStatus();
+        }
+    }, 2000);
+});
+
+async function loadServers() {
+    try {
+        const servers = await invoke('fetch_servers');
+        const select = document.getElementById('serverSelect');
+        select.innerHTML = '';
+        
+        servers.forEach(server => {
+            const option = document.createElement('option');
+            option.value = server;
+            option.textContent = server;
+            select.appendChild(option);
+        });
+    } catch (error) {
+        console.error('Failed to load servers:', error);
+        showError('Failed to load server list');
+    }
+}
+
+async function toggleConnection() {
+    const button = document.getElementById('connectButton');
+    const buttonText = document.getElementById('buttonText');
+    
+    button.disabled = true;
+    buttonText.textContent = 'Connecting...';
+    
+    try {
+        if (!isConnected) {
+            const response = await invoke('connect_vpn');
+            console.log('Connect response:', response);
+            isConnected = true;
+            updateUI(true);
+        } else {
+            const response = await invoke('disconnect_vpn');
+            console.log('Disconnect response:', response);
+            isConnected = false;
+            updateUI(false);
+        }
+    } catch (error) {
+        console.error('Connection error:', error);
+        showError(error);
+    } finally {
+        button.disabled = false;
+    }
+}
+
+function updateUI(connected) {
+    const button = document.getElementById('connectButton');
+    const buttonText = document.getElementById('buttonText');
+    const statusIndicator = document.getElementById('statusIndicator');
+    const statsGrid = document.getElementById('statsGrid');
+    
+    if (connected) {
+        button.classList.add('connected');
+        buttonText.textContent = 'Disconnect';
+        statusIndicator.textContent = 'Connected';
+        statusIndicator.classList.add('connected');
+        statsGrid.style.display = 'grid';
+    } else {
+        button.classList.remove('connected');
+        buttonText.textContent = 'Connect';
+        statusIndicator.textContent = 'Disconnected';
+        statusIndicator.classList.remove('connected');
+        statsGrid.style.display = 'none';
+    }
+}
+
+async function updateStatus() {
+    if (!isConnected) return;
+    
+    try {
+        const status = await invoke('get_status');
+        const data = JSON.parse(status);
+        
+        // Update stats
+        document.getElementById('uploadSpeed').textContent = formatSpeed(data.upload_speed);
+        document.getElementById('downloadSpeed').textContent = formatSpeed(data.download_speed);
+        document.getElementById('ping').textContent = `${data.ping} ms`;
+    } catch (error) {
+        console.error('Failed to update status:', error);
+    }
+}
+
+function formatSpeed(bytesPerSecond) {
+    if (bytesPerSecond < 1024) {
+        return `${bytesPerSecond} B/s`;
+    } else if (bytesPerSecond < 1024 * 1024) {
+        return `${(bytesPerSecond / 1024).toFixed(1)} KB/s`;
+    } else {
+        return `${(bytesPerSecond / (1024 * 1024)).toFixed(2)} MB/s`;
+    }
+}
+
+function showSettings() {
+    alert('Settings panel coming soon!');
+}
+
+function showError(message) {
+    // TODO: Better error UI
+    alert(`Error: ${message}`);
+}