fix(ui): resolve disabled state cursor regression and add dropdown tests

frontend/src/components/ui/button.test.tsx

@@ -18,4 +18,14 @@ describe("Button component", () => {
     button = screen.getByRole("button", { name: /destructive/i })
     expect(button).toHaveClass("cursor-pointer")
   })
+
+  it("renders with a default cursor when disabled", () => {
+    render(<Button disabled>Disabled Button</Button>)
+    const button = screen.getByRole("button", { name: /disabled button/i })
+    expect(button).toBeDisabled()
+    // It should have cursor-pointer but also disabled:pointer-events-none 
+    // which prevents the cursor from changing. 
+    // We can also add disabled:cursor-default for clarity.
+    expect(button).toHaveClass("disabled:pointer-events-none")
+  })
 })