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-daemon/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "ostp-daemon"
+version.workspace = true
+edition.workspace = true
+description = "OSTP Windows Service - Background VPN Daemon"
+
+[[bin]]
+name = "ostp-daemon"
+path = "src/main.rs"
+
+[dependencies]
+ostp = { path = "../ostp" }
+osn = { path = "../osn" }
+osds = { path = "../osds" }
+tokio.workspace = true
+anyhow.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+
+# Windows-specific
+[target.'cfg(windows)'.dependencies]
+windows-service = "0.7"
+winapi = { version = "0.3", features = ["winsvc", "winbase", "processthreadsapi", "namedpipeapi", "fileapi", "handleapi", "minwindef"] }