Move favicon assets from lib/assets/ to web/ and wire up HTML/manifest

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

frontend/web/index.html

@@ -24,10 +24,12 @@
   <meta name="mobile-web-app-capable" content="yes">
   <meta name="apple-mobile-web-app-status-bar-style" content="black">
   <meta name="apple-mobile-web-app-title" content="frontend">
-  <link rel="apple-touch-icon" href="icons/Icon-192.png">
+  <link rel="apple-touch-icon" href="icons/apple-touch-icon.png">
 
   <!-- Favicon -->
-  <link rel="icon" type="image/png" href="favicon.png"/>
+  <link rel="icon" type="image/x-icon" href="favicon.ico"/>
+  <link rel="icon" type="image/png" sizes="16x16" href="icons/favicon-16x16.png"/>
+  <link rel="icon" type="image/png" sizes="32x32" href="icons/favicon-32x32.png"/>
 
   <title>frontend</title>
   <link rel="manifest" href="manifest.json">

frontend/web/manifest.json

@@ -10,12 +10,12 @@
     "prefer_related_applications": false,
     "icons": [
         {
-            "src": "icons/Icon-192.png",
+            "src": "icons/android-chrome-192x192.png",
             "sizes": "192x192",
             "type": "image/png"
         },
         {
-            "src": "icons/Icon-512.png",
+            "src": "icons/android-chrome-512x512.png",
             "sizes": "512x512",
             "type": "image/png"
         },