Add custom background settings controls

src/app/mod.rs

@@ -2432,6 +2432,35 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
         .spacing(10)
         .width(iced::Length::Fill);
 
+        let remove_background: Element<'_, AppMessage> = if state.config.background.is_some() {
+            button(text("Remove background").size(13))
+                .on_press(AppMessage::RemoveBackground)
+                .style(b_style(color_surface, color_blue, color_text, 6.0))
+                .padding(8)
+                .into()
+        } else {
+            iced::widget::Space::new().width(0.0).height(0.0).into()
+        };
+        let background_section = column![
+            row![
+                button(text("Choose image…").size(13))
+                    .on_press(AppMessage::PickBackgroundFile)
+                    .style(b_style(color_surface, color_blue, color_text, 6.0))
+                    .padding(8),
+                remove_background,
+            ].spacing(8),
+            text(format!("Background dimming: {:.0}%", state.config.background_dim * 100.0))
+                .size(11)
+                .color(color_subtext),
+            slider(0.0..=1.0, state.config.background_dim, AppMessage::SetBackgroundDim)
+                .step(0.05),
+            text("Set a picture from your computer as the app background. Auto-resized; a dimming overlay keeps text readable. Applies live.")
+                .size(11)
+                .color(color_subtext),
+        ]
+        .spacing(10)
+        .width(iced::Length::Fill);
+
         // Inline avatar chooser (W4): the monogram fallback plus the bundled
         // presets, each a clickable tile. Same SelectAvatar message, applied live
         // + persisted (and re-announced to the room).
@@ -2780,6 +2809,9 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
                 vertical_space(section_gap),
                 section_header("Theme"),
                 theme_section,
+                vertical_space(section_gap),
+                section_header("Background"),
+                background_section,
             ]
             .spacing(10)
             .width(iced::Length::Fill)