feat: add recipe theme and resume controls

Fixes #4, #7

README.md

@@ -33,6 +33,11 @@ the best use of the available screen while keeping all recipe content visible.
 The recipe title, timing metadata, yield, and QR controller remain at fixed
 sizes.
 
+`theme` defaults to `"dark"`. Set it to `"light"` for a light starting theme;
+the controller and recipe overlay also offer a toggle, and the chosen theme is
+saved locally. After exiting recipe mode, use **Resume last recipe** in the
+controller to restore its portions and completion marks.
+
 When portions change, the display shows both the selected yield and the
 recipe's original yield. Ingredients without a leading quantity are marked in
 yellow because they cannot be scaled; unsupported or imprecise numeric scaling