chore: 添加缺失的静态资源文件

添加多个前端界面所需的图片、字体、音频等静态资源文件，包括：
- 管理员后台的图标、背景图、组件图片
- 移动端页面的商品图片、用户中心图片、活动图标
- 第三方库的示例图片和字体文件
- 浏览器兼容性配置文件
- 图标字体文件（eot、ttf、woff、woff2格式）

这些资源是前端界面正常显示所必需的，之前可能因版本控制忽略或遗漏而缺失。

vendor/symfony/mime/Part/AbstractPart.php

@@ -0,0 +1,65 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mime\Part;
+
+use Symfony\Component\Mime\Header\Headers;
+
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+abstract class AbstractPart
+{
+    private $headers;
+
+    public function __construct()
+    {
+        $this->headers = new Headers();
+    }
+
+    public function getHeaders(): Headers
+    {
+        return $this->headers;
+    }
+
+    public function getPreparedHeaders(): Headers
+    {
+        $headers = clone $this->headers;
+        $headers->setHeaderBody('Parameterized', 'Content-Type', $this->getMediaType().'/'.$this->getMediaSubtype());
+
+        return $headers;
+    }
+
+    public function toString(): string
+    {
+        return $this->getPreparedHeaders()->toString()."\r\n".$this->bodyToString();
+    }
+
+    public function toIterable(): iterable
+    {
+        yield $this->getPreparedHeaders()->toString();
+        yield "\r\n";
+        yield from $this->bodyToIterable();
+    }
+
+    public function asDebugString(): string
+    {
+        return $this->getMediaType().'/'.$this->getMediaSubtype();
+    }
+
+    abstract public function bodyToString(): string;
+
+    abstract public function bodyToIterable(): iterable;
+
+    abstract public function getMediaType(): string;
+
+    abstract public function getMediaSubtype(): string;
+}