feat(ui): /companies Hero logo 换成建材 logo 图片

去掉公司名首字'中'占位, 改用 public/images/logo.png(建材 logo)
图片 object-fit contain 不裁切

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

offer_frontend/src/views/portal/CompanyListView.vue

@@ -4,6 +4,9 @@
     <!-- ① 总院 Hero -->
     <section class="hero-section">
       <div class="hero-inner">
+        <div class="hero-logo">
+          <img :src="group.logo || '/images/logo.png'" alt="logo" />
+        </div>
         <div class="hero-content">
           <h1 class="hero-name hero-name-link" @click="$router.push(`/companies/${group.id}`)">{{ group.name }}</h1>
           <div class="hero-meta">
@@ -170,6 +173,27 @@ onMounted(async () => {
   gap: 36px;
   align-items: flex-start;
 }
+.hero-logo {
+  flex-shrink: 0;
+  width: 96px;
+  height: 96px;
+  border-radius: 4px;
+  overflow: hidden;
+  border: 1px solid var(--border);
+  background: var(--bg-page);
+}
+.hero-logo img { width: 100%; height: 100%; object-fit: contain; padding: 8px; }
+.logo-placeholder {
+  width: 100%;
+  height: 100%;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  font-family: var(--serif);
+  font-size: 36px;
+  font-weight: 700;
+  color: var(--brand-red);
+}
 .hero-name {
   font-family: var(--serif);
   font-size: 28px;