Extract and apply StartupWMClass for proper taskbar icons

Parse StartupWMClass from embedded .desktop entries during analysis,
store in DB, include in generated .desktop files. Detail view shows
an editable WM class field with apply button for manual override.

src/core/inspector.rs

@@ -61,6 +61,7 @@ pub struct AppImageMetadata {
     pub desktop_actions: Vec<String>,
     pub has_signature: bool,
     pub screenshot_urls: Vec<String>,
+    pub startup_wm_class: Option<String>,
 }
 
 #[derive(Debug, Default)]
@@ -76,6 +77,7 @@ struct DesktopEntryFields {
     mime_types: Vec<String>,
     terminal: bool,
     x_appimage_name: Option<String>,
+    startup_wm_class: Option<String>,
     actions: Vec<String>,
 }
 
@@ -367,6 +369,7 @@ fn parse_desktop_entry(content: &str) -> DesktopEntryFields {
                 }
                 "Terminal" => fields.terminal = value == "true",
                 "X-AppImage-Name" => fields.x_appimage_name = Some(value.to_string()),
+                "StartupWMClass" => fields.startup_wm_class = Some(value.to_string()),
                 "Actions" => {
                     fields.actions = value
                         .split(';')
@@ -814,6 +817,7 @@ pub fn inspect_appimage(
             .as_ref()
             .map(|a| a.screenshot_urls.clone())
             .unwrap_or_default(),
+        startup_wm_class: fields.startup_wm_class,
     })
 }