feat(settings): add Rebuild & Install self-update button

Settings panel now shows the current version and a "Rebuild & Install
Latest" button that:
  1. git pull from the embedded source directory (CARGO_MANIFEST_DIR)
  2. makepkg -sf in packaging/
  3. pkexec pacman -U (graphical polkit auth prompt)

Reports the installed version on success; surfaces the failing step on
error. Update runs off the UI thread so the window stays responsive.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/gui.rs

@@ -61,6 +61,9 @@ pub enum Message {
     ServiceInstall,
     ServiceUninstall,
     ServiceActionDone(Result<(), String>),
+    // Self-update
+    UpdateApp,
+    UpdateAppDone(Result<String, String>),
 }
 
 struct Dashboard {
@@ -87,6 +90,8 @@ struct Dashboard {
     proton_versions: Vec<String>,
     service_busy: bool,
     service_status: String,
+    update_busy: bool,
+    update_status: String,
 }
 
 impl Dashboard {
@@ -118,6 +123,8 @@ impl Dashboard {
             proton_versions,
             service_busy: false,
             service_status: String::new(),
+            update_busy: false,
+            update_status: String::new(),
         }
     }
 }
@@ -570,6 +577,22 @@ fn update(state: &mut Dashboard, msg: Message) -> Task<Message> {
             }
             Task::none()
         }
+        Message::UpdateApp => {
+            state.update_busy = true;
+            state.update_status = "Pulling latest changes…".into();
+            Task::perform(
+                async_blocking(run_self_update),
+                Message::UpdateAppDone,
+            )
+        }
+        Message::UpdateAppDone(res) => {
+            state.update_busy = false;
+            state.update_status = match res {
+                Ok(ver) => format!("✓ Updated to {ver} — restart the app to apply."),
+                Err(e) => format!("Update failed: {e}"),
+            };
+            Task::none()
+        }
     }
 }
 
@@ -1155,6 +1178,18 @@ fn view_settings(state: &Dashboard) -> Element<'_, Message> {
         text(svc_status_label).size(13),
         row![svc_install_btn, svc_uninstall_btn,].spacing(10),
         text(&state.service_status).size(12),
+        iced::widget::horizontal_rule(1),
+        row![
+            text(format!("Version: {}", env!("CARGO_PKG_VERSION"))).size(13),
+            iced::widget::horizontal_space(),
+        ]
+        .align_y(Alignment::Center),
+        button(
+            text(if state.update_busy { "Updating…" } else { "Rebuild & Install Latest" }).size(13),
+        )
+        .on_press_maybe((!state.update_busy).then_some(Message::UpdateApp))
+        .style(button::secondary),
+        text(&state.update_status).size(12),
     ]
     .spacing(10)
     .padding(20);
@@ -1165,6 +1200,67 @@ fn view_settings(state: &Dashboard) -> Element<'_, Message> {
         .into()
 }
 
+fn run_self_update() -> Result<String, String> {
+    let src = std::path::Path::new(env!("CARGO_MANIFEST_DIR"));
+    if !src.exists() {
+        return Err(format!("Source directory not found: {}", src.display()));
+    }
+    let pkg_dir = src.join("packaging");
+
+    // 1. git pull
+    let out = std::process::Command::new("git")
+        .args(["-C", src.to_str().unwrap_or("."), "pull"])
+        .output()
+        .map_err(|e| format!("git pull: {e}"))?;
+    if !out.status.success() {
+        return Err(format!("git pull failed: {}", String::from_utf8_lossy(&out.stderr)));
+    }
+
+    // 2. makepkg -sf --noconfirm
+    let out = std::process::Command::new("makepkg")
+        .args(["-sf", "--noconfirm"])
+        .current_dir(&pkg_dir)
+        .output()
+        .map_err(|e| format!("makepkg: {e}"))?;
+    if !out.status.success() {
+        return Err(format!("makepkg failed: {}", String::from_utf8_lossy(&out.stderr)));
+    }
+
+    // 3. Find the freshly built package
+    let pkg = std::fs::read_dir(&pkg_dir)
+        .map_err(|e| e.to_string())?
+        .flatten()
+        .filter_map(|e| {
+            let name = e.file_name();
+            let n = name.to_string_lossy().to_string();
+            if n.ends_with(".pkg.tar.zst") && !n.contains("debug") {
+                Some(e.path())
+            } else {
+                None
+            }
+        })
+        .max_by_key(|p| p.metadata().and_then(|m| m.modified()).ok())
+        .ok_or_else(|| "No .pkg.tar.zst found after makepkg".to_string())?;
+
+    // 4. Install with pkexec (graphical auth prompt)
+    let out = std::process::Command::new("pkexec")
+        .args(["pacman", "-U", "--noconfirm", pkg.to_str().unwrap_or("")])
+        .output()
+        .map_err(|e| format!("pkexec: {e}"))?;
+    if !out.status.success() {
+        return Err(format!("Install failed: {}", String::from_utf8_lossy(&out.stderr)));
+    }
+
+    // Extract version from package filename e.g. umutray-0.1.0-4-x86_64.pkg.tar.zst
+    let ver = pkg
+        .file_name()
+        .and_then(|n| n.to_str())
+        .and_then(|n| n.split('-').nth(1))
+        .unwrap_or("?")
+        .to_string();
+    Ok(ver)
+}
+
 pub fn run(config: &Config) -> Result<()> {
     let config = config.clone();
     iced::application(|_: &Dashboard| String::from("umutray"), update, view)