feat: 앱 아이콘·파비콘을 '돈돼지' 이미지로 변경

- piggy-fg.png(투명 전경)에서 icon-foreground/background(금색)/only 합성
- @capacitor/assets generate --android 로 안드로이드 런처/적응형 아이콘 재생성
- 파비콘: public/favicon.png·apple-touch-icon.png 생성, index.html 갱신(구 logo.svg→png)
- PC(Electron) 설치 아이콘은 icon-only.png 사용(설치파일 재빌드 시 반영)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

android/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@mipmap/ic_launcher_background" />
-    <foreground android:drawable="@mipmap/ic_launcher_foreground" />
+    <background>
+        <inset android:drawable="@mipmap/ic_launcher_background" android:inset="16.7%" />
+    </background>
+    <foreground>
+        <inset android:drawable="@mipmap/ic_launcher_foreground" android:inset="16.7%" />
+    </foreground>
 </adaptive-icon>

android/app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@mipmap/ic_launcher_background" />
-    <foreground android:drawable="@mipmap/ic_launcher_foreground" />
+    <background>
+        <inset android:drawable="@mipmap/ic_launcher_background" android:inset="16.7%" />
+    </background>
+    <foreground>
+        <inset android:drawable="@mipmap/ic_launcher_foreground" android:inset="16.7%" />
+    </foreground>
 </adaptive-icon>