refactor: 死代码清理 + CDN SRI 加固 + 面包屑组件 + 代码规范文档

- 删除 7 个死模板文件 (products/services/quality/process/projects/customization/rfq)
- 删除 13 个旧图片素材 (jpg/png/webp)
- 新增 CDN SRI 完整性校验 (Bootstrap CSS/JS)
- 新增面包屑导航模板组件
- 新增代码清理方案与代码审查标准文档
- 更新 README.md

assets/css/theme.css

@@ -1151,11 +1151,14 @@ textarea:focus-visible {
 .breadcrumb-nav {
   color: var(--b2b-ink-muted);
   font-size: 0.9rem;
+  line-height: 1.6;
+  word-break: break-word;
 }
 
 .breadcrumb-nav a {
   color: var(--b2b-ink-soft);
   text-decoration: none;
+  white-space: normal;
 }
 
 .breadcrumb-nav a:hover {
@@ -1304,14 +1307,87 @@ textarea:focus-visible {
 
 /* XL down — 1199px */
 @media (max-width: 1199px) {
-  .b2b-header .offcanvas-body {
-    display: block;
-    padding: 2rem;
+  /* Offcanvas mobile menu */
+  .b2b-header .offcanvas {
+    max-width: 320px;
+    width: 85vw !important;
+    height: 100dvh;
+    height: 100vh;
+    overflow-y: auto;
+    background: var(--b2b-surface);
+    border-left: 1px solid var(--b2b-line-light);
+    box-shadow: var(--b2b-shadow-lg, 0 0 30px rgba(28,28,26,0.08));
   }
 
+  .b2b-header .offcanvas-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    flex-shrink: 0;
+    border-bottom: 1px solid var(--b2b-line-light);
+    padding: 1.25rem 1.5rem;
+    margin: 0;
+  }
+
+  .b2b-header .offcanvas-title {
+    font-weight: 600;
+    font-size: 1.1rem;
+    color: var(--b2b-ink);
+  }
+
+  .b2b-header .offcanvas-body {
+    flex: 1 1 auto;
+    display: flex !important;
+    flex-direction: column;
+    padding: 0.5rem 1.5rem 2rem;
+    overflow-y: auto;
+  }
+
+  .b2b-header .offcanvas .navbar-nav {
+    display: flex !important;
+    flex-direction: column;
+    gap: 0;
+    margin: 0 0 1.5rem 0;
+    padding: 0;
+    list-style: none;
+    width: 100%;
+  }
+
+  .b2b-header .offcanvas .nav-item {
+    border-bottom: 1px solid var(--b2b-line-light);
+    width: 100%;
+  }
+
+  .b2b-header .offcanvas .nav-link {
+    display: block;
+    width: 100%;
+    padding: 0.85rem 0;
+    color: var(--b2b-ink);
+    font-size: 1.05rem;
+    font-weight: 500;
+    text-align: left;
+    text-decoration: none;
+    transition: color 180ms ease;
+  }
+
+  .b2b-header .offcanvas .nav-link:hover,
+  .b2b-header .offcanvas .nav-link:focus {
+    color: var(--b2b-ink-soft);
+  }
+
+  .b2b-header .offcanvas .nav-link.active,
+  .b2b-header .offcanvas .current-menu-item > .nav-link {
+    color: var(--b2b-ink);
+    font-weight: 600;
+  }
+
+  .b2b-header .b2b-header-cta {
+    align-self: flex-start;
+  }
+
+  /* Navbar layout overrides for collapsed state */
   .b2b-header .navbar-nav {
     gap: 1.25rem;
-    margin-bottom: 1.5rem;
   }
 
   .capability-grid {