feat: enhance image handling and analytics configuration

- Add @unpic/astro for improved image optimization
- Configure image service with blurhash placeholder
- Update analytics script to support custom JavaScript URLs
- Modify preload configuration for more flexible analytics integration
- Remove deprecated rehype image transformation plugin

src/types/index.d.ts

@@ -79,8 +79,7 @@ export interface ThemeConfig {
   preload: {
     commentURL?: string
     imageHostURL?: string
-    customGoogleAnalyticsURL?: string
-    customUmamiAnalyticsURL?: string
+    customGoogleAnalyticsJS?: string
     customUmamiAnalyticsJS?: string
   }
 }