Pptx/Render: picture fills with rotWithShape=0 stay upright

A shape's picture fill marked not to rotate with the shape turned and
flipped with it (rotWithShape was neither kept nor written: always 1).
PowerPoint keeps such a picture upright, stretched (or tiled) over the
box the rotated shape covers on the slide and clipped to the shape. Now
read, written (PictureFill::upright) and drawn so.

Wild synthetic set: picture fills on rotated/flipped shapes 12.89 ->
3.87.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/model/src/style.rs

@@ -139,6 +139,10 @@ pub struct PictureFill {
     /// 0–1 opacity of the picture.
     pub alpha: Option<f64>,
     pub adjust: PictureAdjust,
+    /// `rotWithShape="0"`: the picture keeps to the slide's axes when its shape is rotated or
+    /// flipped.
+    #[serde(skip_serializing_if = "std::ops::Not::not")]
+    pub upright: bool,
 }
 
 /// Picture corrections and colour (Picture Format ▸ Corrections / Color / Transparency).