Remove custom Mermaid viewBox fix and switch to unpkg for assets

Switch Mermaid CDN to unpkg and add footer with ICP info

hugo.yaml

@@ -82,6 +82,7 @@ params:
     displayCopyright: true
     displayPoweredBy: false
     width: normal
+    icp: "粤ICP备2026061516号"
 
   # 日期
   displayUpdatedDate: false
@@ -94,6 +95,7 @@ params:
     flexsearch:
       index: content
       tokenize: forward
+      base: "https://unpkg.com/flexsearch@0.7.43/dist"
 
   # 博客
   blog:
@@ -138,7 +140,9 @@ params:
 
   # Mermaid 流程图（本地加载，避免 CDN 连接问题）
   mermaid:
-    base: "https://cdn.jsdelivr.net/npm/mermaid@11.15.0/dist"
+    base: "https://unpkg.com/mermaid@11.4.1/dist"
+    lightTheme: neutral
+    darkTheme: dark
 
   # Open Graph / SEO 增强
   opengraph: