refactor: remove dead code and #[allow(dead_code)] annotations

Removed unused sync podman_command/docker_command methods.
Removed dead_code annotations from User and AuthManager (now actively used).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/container/src/runtime.rs

@@ -99,15 +99,6 @@ impl DockerRuntime {
         cmd
     }
 
-    #[allow(dead_code)]
-    fn docker_command(&self) -> Command {
-        let mut cmd = Command::new("docker");
-        // Use actual HOME environment variable instead of hardcoded /home
-        if let Ok(home) = std::env::var("HOME") {
-            cmd.env("HOME", home);
-        }
-        cmd
-    }
 }
 
 #[async_trait]