Serve the MealQuest favicon instead of the browser default (Maestro 7c778111)

index.html linked only the apple-touch-icon, so browsers fell back to a
default favicon. generate-icons now also writes favicon.ico (16/32/48
PNG-in-ICO) and 16/32 px PNG favicons from the v1 logo; index.html links
them, and the service worker precaches every icon and favicon so the
offline shell keeps them (the glob covers the manifest icons, so the
plugin no longer injects them a second time).

pwa.test.ts asserts the build ships the favicons at the right sizes,
links them from index.html, and precaches each icon exactly once.

Task: 7c778111-c615-4437-a3f6-0e36bcb97e63

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/index.html

@@ -4,6 +4,9 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <meta name="theme-color" content="#5a358c" />
+    <link rel="icon" href="/favicon.ico" sizes="16x16 32x32 48x48" />
+    <link rel="icon" type="image/png" sizes="32x32" href="/icons/favicon-32.png" />
+    <link rel="icon" type="image/png" sizes="16x16" href="/icons/favicon-16.png" />
     <link rel="apple-touch-icon" href="/apple-touch-icon.png" />
     <title>MealQuest</title>
   </head>