refactor: rename aim to upm and extract appimage module

crates/upm-core/tests/install_scope.rs

@@ -0,0 +1,8 @@
+use upm_core::app::scope::{ScopeOverride, resolve_install_scope};
+use upm_core::domain::app::InstallScope;
+
+#[test]
+fn explicit_scope_override_beats_effective_user() {
+    let scope = resolve_install_scope(false, ScopeOverride::System);
+    assert_eq!(scope, InstallScope::System);
+}