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/src/state.rs

@@ -0,0 +1,37 @@
+//! Application state management
+
+use std::sync::{Arc, Mutex};
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ConnectionStatus {
+    pub connected: bool,
+    pub server: Option<String>,
+    pub upload_speed: u64,
+    pub download_speed: u64,
+    pub ping: u32,
+}
+
+impl Default for ConnectionStatus {
+    fn default() -> Self {
+        Self {
+            connected: false,
+            server: None,
+            upload_speed: 0,
+            download_speed: 0,
+            ping: 0,
+        }
+    }
+}
+
+pub struct AppState {
+    pub status: Arc<Mutex<ConnectionStatus>>,
+}
+
+impl AppState {
+    pub fn new() -> Self {
+        Self {
+            status: Arc::new(Mutex::new(ConnectionStatus::default())),
+        }
+    }
+}