refactor(core/rust): fix Layout::return_value() after Error is no longer Clone

### core/embed/rust/src/ui/api/firmware_micropython.rs
@@ -1438,8 +1438,13 @@ pub static mp_module_trezorui_api: Module = obj_module! {
     ///     def get_transition_out(self) -> AttachType:
     ///         """Return the transition type."""
     ///
-    ///     def return_value(self) -> T:
-    ///         """Retrieve the return value of the layout object."""
+    ///     def return_value(self) -> T | None:
+    ///         """Take the return value of the layout object.
+    ///
+    ///         Not idempotent: after `return_value()` is called, subsequent calls will return None.
+    ///
+    ///         May raise in case there was an error when constructing the return value.
+    ///         """
     ///
     ///     # TODO: remove after https://github.com/trezor/trezor-firmware/issues/6811 is resolved.
     ///     def __del__(self) -> None:

### core/embed/rust/src/ui/flow/swipe.rs
@@ -282,7 +282,9 @@ impl SwipeFlow {
 /// This way we can completely avoid implementing `Component`. That also allows
 /// us to pass around concrete Renderers instead of having to conform to
 /// `Component`'s not-object-safe interface.
-impl Layout<Result<Obj, Error>> for SwipeFlow {
+impl Layout for SwipeFlow {
+    type Value = Result<Obj, Error>;
+
     fn place(&mut self) {
         for elem in self.store.iter_mut() {
             elem.place(ModelUI::SCREEN);
@@ -293,8 +295,8 @@ impl Layout<Result<Obj, Error>> for SwipeFlow {
         self.event(ctx, event)
     }
 
-    fn value(&self) -> Option<&Result<Obj, Error>> {
-        self.returned_value.as_ref()
+    fn take_value(&mut self) -> Option<Self::Value> {
+        self.returned_value.take()
     }
 
     fn paint(&mut self) -> Result<(), PaintOutOfBounds> {

### core/embed/rust/src/ui/layout/base.rs
@@ -12,10 +12,12 @@ pub enum LayoutState {
 
 pub struct PaintOutOfBounds;
 
-pub trait Layout<T> {
+pub trait Layout {
+    type Value;
+
     fn place(&mut self);
     fn event(&mut self, ctx: &mut EventCtx, event: Event) -> Option<LayoutState>;
-    fn value(&self) -> Option<&T>;
+    fn take_value(&mut self) -> Option<Self::Value>;
     fn paint(&mut self) -> Result<(), PaintOutOfBounds>;
 }
 

### core/embed/rust/src/ui/layout/obj.rs
@@ -115,10 +115,12 @@ where
     }
 }
 
-impl<T> Layout<Result<Obj, Error>> for RootComponent<T, ModelUI>
+impl<T> Layout for RootComponent<T, ModelUI>
 where
     T: Component + ComponentMsgObj,
 {
+    type Value = Result<Obj, Error>;
+
     fn place(&mut self) {
         self.inner.place(ModelUI::SCREEN);
     }
@@ -134,8 +136,8 @@ where
         }
     }
 
-    fn value(&self) -> Option<&Result<Obj, Error>> {
-        self.returned_value.as_ref()
+    fn take_value(&mut self) -> Option<Self::Value> {
+        self.returned_value.take()
     }
 
     fn paint(&mut self) -> Result<(), PaintOutOfBounds> {
@@ -168,8 +170,8 @@ where
     }
 }
 
-pub trait LayoutMaybeTrace: Layout<Result<Obj, Error>> + MaybeTrace {}
-impl<T> LayoutMaybeTrace for T where T: Layout<Result<Obj, Error>> + MaybeTrace {}
+pub trait LayoutMaybeTrace: Layout<Value = Result<Obj, Error>> + MaybeTrace {}
+impl<T> LayoutMaybeTrace for T where T: Layout<Value = Result<Obj, Error>> + MaybeTrace {}
 
 #[derive(Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "debug", derive(ufmt::derive::uDebug))]
@@ -364,10 +366,9 @@ impl LayoutObjInner {
         self.transition_out.to_obj()
     }
 
-    fn obj_return_value(&self) -> Result<Obj, Error> {
-        self.root()?
-            .value()
-            .cloned()
+    fn obj_return_value(&mut self) -> Result<Obj, Error> {
+        self.root_mut()?
+            .take_value()
             .unwrap_or(Ok(Obj::const_none()))
     }
 }
@@ -629,11 +630,11 @@ extern "C" fn ui_layout_timer(this: Obj, token: Obj) -> Obj {
 extern "C" fn ui_layout_paint(this: Obj) -> Obj {
     let block = || {
         let this: Gc<LayoutObj> = this.try_into()?;
-        let painted = this.inner_mut().obj_paint_if_requested();
-        if painted? {
+        let painted = this.inner_mut().obj_paint_if_requested()?;
+        if painted {
             display::refresh();
         }
-        Ok(painted?.into())
+        Ok(painted.into())
     };
     unsafe { util::try_or_raise(block) }
 }

### core/mocks/generated/trezorui_api.pyi
@@ -76,8 +76,11 @@ class LayoutObj(Generic[T]):
         """Return (code, type) of button request made during the last event or timer pass."""
     def get_transition_out(self) -> AttachType:
         """Return the transition type."""
-    def return_value(self) -> T:
-        """Retrieve the return value of the layout object."""
+    def return_value(self) -> T | None:
+        """Take the return value of the layout object.
+        Not idempotent: after `return_value()` is called, subsequent calls will return None.
+        May raise in case there was an error when constructing the return value.
+        """
     # TODO: remove after https://github.com/trezor/trezor-firmware/issues/6811 is resolved.
     def __del__(self) -> None:
         """Calls drop on contents of the root component."""