refactor(src/daemon): replace execute calls with execute_local for dbus commands

Why: Adopt local execution path to streamline command handling and reduce RPC overhead.

New Features
-

Enhancements
- Replace `gpu::execute` with `gpu::execute_local` in integrated, hybrid, and nvidia command invocations.
- Replace `crate::commands::power`, `battery`, `cooling`, and `touchpad` executions with `execute_local`.
- Remove the unused `LAPCTL_DAEMON_INTERNAL` environment variable setting.

Bug Fixes
- None

src/daemon/mod.rs

@@ -6,9 +6,6 @@ mod dbus_iface;
 
 pub async fn run() -> Result<(), Box<dyn Error>> {
     info!("Starting lapctld daemon...");
-    unsafe {
-        std::env::set_var("LAPCTL_DAEMON_INTERNAL", "1");
-    }
     let _connection = Builder::system()?
         .name("org.lapctl")?
         .serve_at("/org/lapctl", dbus_iface::LapctlInterface::default())?