fix: image caching issues

1. Fix cache name mismatch: imageCacheService now uses 'boris-images'
   to match the Service Worker cache name
2. Remove cross-origin restriction: Cache ALL images, not just
   cross-origin ones. This ensures article images from any source
   are cached by the Service Worker
3. Update comments to clarify Service Worker caching behavior

Images should now be properly cached when loaded via <img> tags.

src/hooks/useImageCache.ts

@@ -10,6 +10,8 @@ export function useImageCache(
   imageUrl: string | undefined
 ): string | undefined {
   // Service Worker handles everything - just return the URL as-is
+  // The Service Worker will intercept fetch requests and cache them
+  // Make sure images use standard <img src> tags for SW interception
   return imageUrl
 }