fix: load BrowserWindow icon from resources/ in packaged AppImage

The BrowserWindow icon path resolved correctly in dev (`__dirname` =
src-electron/, so `../src-tauri/icons/icon.png` reached the source tree)
but not in the packaged AppImage, where `__dirname` is inside the asar
and src-tauri/ is not bundled. Electron silently dropped the icon and
the taskbar fell back to the generic Electron icon.

Copy icon.png into the AppImage's resources/ via extraResources, and
load it from process.resourcesPath when app.isPackaged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: abose

src-electron/electron-builder.yml

@@ -27,6 +27,8 @@ extraResources:
     to: "bin"
   - from: "phoenix-dist"
     to: "phoenix-dist"
+  - from: "../src-tauri/icons/icon.png"
+    to: "icon.png"
 
 extraMetadata:
   main: main.js

src-electron/main.js

@@ -118,7 +118,9 @@ async function createWindow() {
             contextIsolation: true,
             nodeIntegration: false
         },
-        icon: path.join(__dirname, '..', 'src-tauri', 'icons', 'icon.png')
+        icon: app.isPackaged
+            ? path.join(process.resourcesPath, 'icon.png')
+            : path.join(__dirname, '..', 'src-tauri', 'icons', 'icon.png')
     });
 
     // Track window state for persistence