feat: add favicon (SVG shopping-bag logo + ICO fallback)

Orange #FF5500 rounded-square with shopping-bag icon matching the
sidebar logo. Includes SVG (modern), ICO (16+32px, legacy), and
apple-touch-icon PNG.

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

web/static/favicon.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="32" height="32" viewBox="0 0 32 32">
+  <rect width="32" height="32" rx="8" fill="#FF5500"/>
+  <path d="M10 13h12l-1.8 10H11.8L10 13Z" fill="white" opacity="0.95"/>
+  <path d="M13 13v-2.5a3 3 0 016 0V13" stroke="white" stroke-width="1.8" stroke-linecap="round" fill="none"/>
+  <line x1="13.5" y1="17.5" x2="18.5" y2="17.5" stroke="#FF5500" stroke-width="1.5" stroke-linecap="round"/>
+</svg>

web/templates/base.html

@@ -4,6 +4,9 @@
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>{% block title %}Мои Товары{% endblock %}</title>
+  <link rel="icon" href="/static/favicon.ico" sizes="16x16 32x32" type="image/x-icon">
+  <link rel="icon" href="/static/favicon.svg" type="image/svg+xml">
+  <link rel="apple-touch-icon" href="/static/favicon-32.png">
   <link rel="preconnect" href="https://fonts.googleapis.com">
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
   <link href="https://fonts.googleapis.com/css2?family=Golos+Text:wght@400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap" rel="stylesheet">

web/templates/login.html

@@ -4,6 +4,9 @@
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Вход — Мои Товары</title>
+  <link rel="icon" href="/static/favicon.ico" sizes="16x16 32x32" type="image/x-icon">
+  <link rel="icon" href="/static/favicon.svg" type="image/svg+xml">
+  <link rel="apple-touch-icon" href="/static/favicon-32.png">
   <link rel="preconnect" href="https://fonts.googleapis.com">
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
   <link href="https://fonts.googleapis.com/css2?family=Golos+Text:wght@400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap" rel="stylesheet">