feat: add allow insecure connections toggle in system settings

Block ws:// relay connections and http:// resource loading by default
to prevent browser mixed content warnings. When blocked, resources
show clickable URL links instead of error placeholders so users can
open them manually.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/WebPreview/index.tsx

@@ -1,7 +1,9 @@
 import { useFetchWebMetadata } from '@/hooks/useFetchWebMetadata'
+import { isInsecureUrl } from '@/lib/url'
 import { cn } from '@/lib/utils'
 import { useContentPolicy } from '@/providers/ContentPolicyProvider'
 import { useScreenSize } from '@/providers/ScreenSizeProvider'
+import storage from '@/services/local-storage.service'
 import { useMemo } from 'react'
 import Image from '../Image'
 import ExternalLink from '../ExternalLink'
@@ -27,6 +29,10 @@ export default function WebPreview({
     }
   }, [url])
 
+  if (!storage.getAllowInsecureConnection() && isInsecureUrl(url)) {
+    return null
+  }
+
   if (!autoLoadMedia && !mustLoad) {
     return null
   }