chore: fix compiler warnings

- Add explicit lifetimes to Element return types
- Remove unused imports (Length, button, horizontal_space, icon, Handle, self)
- Mark unused parameter with underscore prefix

This eliminates all 'hiding a lifetime' and 'unused import' warnings.

src/app/mod.rs

@@ -14,8 +14,8 @@ use cosmic::app::{context_drawer, Core};
 use cosmic::cosmic_config::{self, CosmicConfigEntry};
 use cosmic::iced::keyboard::{self, key::Named, Key, Modifiers};
 use cosmic::iced::window;
-use cosmic::iced::{Length, Subscription};
+use cosmic::iced::Subscription;
-use cosmic::widget::{button, horizontal_space, icon, nav_bar};
+use cosmic::widget::nav_bar;
 use cosmic::{Action, Element, Task};
 
 pub use message::AppMessage;
@@ -145,19 +145,19 @@ impl cosmic::Application for Noctua {
         Task::none()
     }
 
-    fn header_start(&self) -> Vec<Element<Self::Message>> {
+    fn header_start(&self) -> Vec<Element<'_, Self::Message>> {
         view::header::header_start(&self.model)
     }
 
-    fn header_end(&self) -> Vec<Element<Self::Message>> {
+    fn header_end(&self) -> Vec<Element<'_, Self::Message>> {
         view::header::header_end(&self.model)
     }
 
-    fn view(&self) -> Element<Self::Message> {
+    fn view(&self) -> Element<'_, Self::Message> {
         view::view(&self.model)
     }
 
-    fn context_drawer(&self) -> Option<context_drawer::ContextDrawer<Self::Message>> {
+    fn context_drawer(&self) -> Option<context_drawer::ContextDrawer<'_, Self::Message>> {
         if !self.core.window.show_context {
             return None;
         }
@@ -171,7 +171,7 @@ impl cosmic::Application for Noctua {
         Some(&self.nav)
     }
 
-    fn footer(&self) -> Option<Element<Self::Message>> {
+    fn footer(&self) -> Option<Element<'_, Self::Message>> {
         Some(view::footer::view(&self.model))
     }
 

src/app/view/header.rs

@@ -12,7 +12,7 @@ use crate::app::model::AppModel;
 use crate::app::ContextPage;
 
 /// Build the left side of the header bar.
-pub fn header_start(model: &AppModel) -> Vec<Element<AppMessage>> {
+pub fn header_start(model: &AppModel) -> Vec<Element<'_, AppMessage>> {
     let has_doc = model.document.is_some();
 
     vec![
@@ -51,7 +51,7 @@ pub fn header_start(model: &AppModel) -> Vec<Element<AppMessage>> {
 }
 
 /// Build the right side of the header bar.
-pub fn header_end(model: &AppModel) -> Vec<Element<AppMessage>> {
+pub fn header_end(_model: &AppModel) -> Vec<Element<'_, AppMessage>> {
     vec![button::icon(icon::from_name("dialog-information-symbolic"))
         .on_press(AppMessage::ToggleContextPage(ContextPage::Properties))
         .into()]

src/app/view/image_viewer.rs

@@ -1,14 +1,14 @@
 //! Zoom and pan on an image.
 //! Forked from cosmic::iced to support external state control.
 
-use cosmic::iced::advanced::widget::{self, tree::{self, Tree}, Widget};
+use cosmic::iced::advanced::widget::{tree::{self, Tree}, Widget};
 use cosmic::iced::advanced::{
     Clipboard, Layout, Shell,
     layout, renderer, image as img_renderer,
 };
 use cosmic::iced::event::{self, Event};
 use cosmic::iced::mouse;
-use cosmic::iced::widget::image::{self, FilterMethod, Handle};
+use cosmic::iced::widget::image::{self, FilterMethod};
 use cosmic::iced::{
     ContentFit, Element, Length, Pixels, Point,
     Radians, Rectangle, Size, Vector,