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/tauri.conf.json

@@ -0,0 +1,43 @@
+{
+  "$schema": "https://schema.tauri.app/config/2.0",
+  "productName": "OSTP VPN",
+  "version": "0.1.0",
+  "identifier": "network.ospab.ostp",
+  "build": {
+    "beforeDevCommand": "",
+    "devUrl": "../ui/index.html",
+    "beforeBuildCommand": "",
+    "frontendDist": "../ui"
+  },
+  "app": {
+    "windows": [
+      {
+        "title": "OSTP VPN",
+        "width": 450,
+        "height": 600,
+        "resizable": false,
+        "fullscreen": false,
+        "decorations": true,
+        "transparent": false,
+        "alwaysOnTop": false
+      }
+    ],
+    "security": {
+      "csp": "default-src 'self'; style-src 'self' 'unsafe-inline'"
+    }
+  },
+  "bundle": {
+    "active": true,
+    "targets": ["msi"],
+    "icon": [
+      "icons/32x32.png",
+      "icons/128x128.png",
+      "icons/icon.ico"
+    ],
+    "windows": {
+      "certificateThumbprint": null,
+      "digestAlgorithm": "sha256",
+      "timestampUrl": ""
+    }
+  }
+}