fix: resolve Windows CI test failures for image downloader

Remove backslash check in generateSafeFilename to prevent false matches on Windows paths
Use filepath.Join in test to ensure cross-platform path compatibility

Author: alexferrari88

lib/images.go

@@ -286,7 +286,7 @@ func (id *ImageDownloader) generateSafeFilename(imageURL string) (string, error)
 	filename := filepath.Base(parsedURL.Path)
 
 	// If no valid filename, generate one from URL patterns
-	if filename == "" || filename == "/" || filename == "." || filename == "\\" {
+	if filename == "" || filename == "/" || filename == "." {
 		filename = "" // Reset to force fallback logic
 
 		// Try to extract from the URL patterns

lib/images_test.go

@@ -430,8 +430,8 @@ func TestUpdateHTMLWithLocalPaths(t *testing.T) {
 <img src="https://example.com/image1.jpg" alt="Same image again">`
 
 	urlToLocalPath := map[string]string{
-		"https://example.com/image1.jpg": "/output/images/post/image1.jpg",
-		"https://example.com/image2.png": "/output/images/post/image2.png",
+		"https://example.com/image1.jpg": filepath.Join("/output", "images", "post", "image1.jpg"),
+		"https://example.com/image2.png": filepath.Join("/output", "images", "post", "image2.png"),
 	}
 
 	updatedHTML := downloader.updateHTMLWithLocalPaths(originalHTML, urlToLocalPath)