fix: explicit apple-touch-icon sizes=180x180 for iOS PWA icon

webapp/tipitaka-web/index.html

@@ -13,7 +13,7 @@
     <meta name="apple-mobile-web-app-capable" content="yes" />
     <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
     <meta name="apple-mobile-web-app-title" content="Tipitaka มจร." />
-    <link rel="apple-touch-icon" href="/apple-touch-icon.png" />
+    <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png" />
 
     <!-- Theme color — dark theme (#1a1a2e) for seamless PWA status bar on Android/iOS -->
     <meta name="theme-color" content="#1a1a2e" />