yoda: cargo fix --lib across all crates — drop ~115 trivial warnings

Auto-applied suggestions (unused imports, _-prefixed unused params,
redundant mutability) on iced_core, iced_widget, iced_runtime, iced_winit,
iced_wgpu, iced_graphics, iced_tiny_skia. From 170 warnings down to 55.

Leyoda 2026 – GPLv3

core/src/element.rs

@@ -1,4 +1,4 @@
-use crate::event::{self, Event};
+use crate::event::Event;
 use crate::id::Id;
 use crate::layout;
 use crate::mouse;