Switch Windows service install to user session scheduled task

Replaces the Windows service installation with a scheduled task that runs in the user's session, enabling proper user idle detection. Updates install.ps1 to remove service management and add scheduled task logic, updates documentation and output messages, and adds the 'windows' crate dependency for future user session support. Adds warnings to windows_service.rs about idle detection limitations when running as a Windows service.

Author: erdemgoksel

Cargo.lock

@@ -36,6 +36,7 @@ user-idle2 = { git = "https://github.com/ErdemGKSL/user-idle2-rs.git", features
 
 [target.'cfg(windows)'.dependencies]
 windows-service = { version = "0.7", optional = true }
+windows = { version = "0.58", features = ["Win32"] }
 
 [features]
 windows-service = ["dep:windows-service"]