Check arguments for Image()

see https://github.com/collective/icalendar/pull/877#discussion_r2366353004

src/icalendar/prop/image.py

@@ -73,6 +73,10 @@ class Image:
         display: str | None = None,
     ):
         """Create a new image according to :rfc:`7986`."""
+        if uri is not None and b64data is not None:
+            raise ValueError("Image cannot have both URI and binary data (RFC 7986)")
+        if uri is None and b64data is None:
+            raise ValueError("Image must have either URI or binary data")
         self.uri = uri
         self.b64data = b64data
         self.fmttype = fmttype

src/icalendar/tests/test_image.py

@@ -157,3 +157,11 @@ def test_create_image_with_vText_as_binary():
     assert img.fmttype is None
     assert img.altrep is None
     assert img.display is None
+
+
+def test_requires_uri_xor_binary():
+    """Test forbidden parameter combinations."""
+    with pytest.raises(ValueError):
+        Image()
+    with pytest.raises(ValueError):
+        Image(b64data="", uri="http://example.com/image.png")