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-installer/ostp-installer.manifest

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+  <assemblyIdentity
+    version="1.0.0.0"
+    processorArchitecture="amd64"
+    name="OspabInstaller"
+    type="win32"
+  />
+  <description>OSTP Installer</description>
+  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
+    <security>
+      <requestedPrivileges>
+        <requestedExecutionLevel level="requireAdministrator" uiAccess="false"/>
+      </requestedPrivileges>
+    </security>
+  </trustInfo>
+</assembly>