Give the page an icon

An SVG favicon in the page's accent colour, three bars like report rows,
embedded with the rest of static/ so there is still nothing else to deploy.

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

internal/web/static/index.html

@@ -4,6 +4,7 @@
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <title>money</title>
+<link rel="icon" href="icon.svg" type="image/svg+xml">
 <link rel="stylesheet" href="style.css">
 </head>
 <body>