feat: 添加浏览器标签图标 favicon

- 创建 SVG 格式 favicon（深色背景+大脑/网络节点设计）
- 在所有后台管理页面添加 favicon

admin/templates/auto-profiles.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Auto配置管理 - LLM Proxy</title>
+    <link rel="icon" href="/static/img/favicon.svg" type="image/svg+xml">
     <script src="https://cdn.tailwindcss.com"></script>
     <link href="https://cdn.jsdelivr.net/npm/remixicon@3.5.0/fonts/remixicon.css" rel="stylesheet">
     <style>

admin/templates/chat.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>对话 - LLM Proxy</title>
+    <link rel="icon" href="/static/img/favicon.svg" type="image/svg+xml">
     <script src="https://cdn.tailwindcss.com"></script>
     <link href="https://cdn.jsdelivr.net/npm/remixicon@3.5.0/fonts/remixicon.css" rel="stylesheet">
     <style>

admin/templates/config.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>系统配置 - LLM Proxy</title>
+    <link rel="icon" href="/static/img/favicon.svg" type="image/svg+xml">
     <script src="https://cdn.tailwindcss.com"></script>
     <link href="https://cdn.jsdelivr.net/npm/remixicon@3.5.0/fonts/remixicon.css" rel="stylesheet">
     <style>

admin/templates/index.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>LLM Proxy - 后台管理</title>
+    <link rel="icon" href="/static/img/favicon.svg" type="image/svg+xml">
     <script src="https://cdn.tailwindcss.com"></script>
     <link href="https://cdn.jsdelivr.net/npm/remixicon@3.5.0/fonts/remixicon.css" rel="stylesheet">
     <style>

admin/templates/logs.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>日志查看 - LLM Proxy</title>
+    <link rel="icon" href="/static/img/favicon.svg" type="image/svg+xml">
     <script src="https://cdn.tailwindcss.com"></script>
     <link href="https://cdn.jsdelivr.net/npm/remixicon@3.5.0/fonts/remixicon.css" rel="stylesheet">
     <style>

admin/templates/models.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>模型管理 - LLM Proxy</title>
+    <link rel="icon" href="/static/img/favicon.svg" type="image/svg+xml">
     <script src="https://cdn.tailwindcss.com"></script>
     <link href="https://cdn.jsdelivr.net/npm/remixicon@3.5.0/fonts/remixicon.css" rel="stylesheet">
     <style>

admin/templates/providers.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>提供商管理 - LLM Proxy</title>
+    <link rel="icon" href="/static/img/favicon.svg" type="image/svg+xml">
     <script src="https://cdn.tailwindcss.com"></script>
     <link href="https://cdn.jsdelivr.net/npm/remixicon@3.5.0/fonts/remixicon.css" rel="stylesheet">
     <style>