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/Cargo.toml

@@ -0,0 +1,32 @@
+[package]
+name = "ostp-installer"
+version.workspace = true
+edition.workspace = true
+description = "OSTP Windows Installer - Setup Wizard"
+
+[[bin]]
+name = "ostp-installer"
+path = "src/main.rs"
+
+[dependencies]
+anyhow.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+
+# Windows-specific
+[target.'cfg(windows)'.dependencies]
+winapi = { version = "0.3", features = [
+    "winuser", "winsvc", "winbase", "processthreadsapi", "handleapi", "errhandlingapi",
+    "securitybaseapi", "winnt"
+] }
+windows = { version = "0.58", features = [
+    "Win32_System_Services",
+    "Win32_Security",
+    "Win32_Foundation",
+    "Win32_Storage_FileSystem",
+    "Win32_System_Registry",
+] }
+
+# GUI for wizard
+native-windows-gui = "1.0"
+native-windows-derive = "1.0"