修复图片下载问题

backend-java/src/test/java/com/nanri/aiimage/modules/similarasin/util/SimilarAsinImageEmbedderTest.java

@@ -177,6 +177,25 @@ class SimilarAsinImageEmbedderTest {
         assertNotNull(req.header("Accept-Language"));
     }
 
+    @Test
+    void amazonImageDownloadCandidatesTrySmallerVariantsWithinRetryBudget() {
+        List<String> candidates = SimilarAsinImageEmbedder.downloadCandidates(
+                "https://m.media-amazon.com/images/I/71AGS2r4JML._AC_SX679_.jpg");
+
+        assertEquals(List.of(
+                "https://m.media-amazon.com/images/I/71AGS2r4JML._AC_SX679_.jpg",
+                "https://m.media-amazon.com/images/I/71AGS2r4JML._AC_SY450_.jpg",
+                "https://m.media-amazon.com/images/I/71AGS2r4JML._AC_SX425_.jpg"), candidates);
+    }
+
+    @Test
+    void downloadCandidatesLeaveNonAmazonAndUnsignedUrlsUntouched() {
+        String coze = "https://lf9-bot-platform-tos-sign.coze.cn/bot-studio-bot-platform/bot_files/1/image/jpeg/2/merged_image.jpg?x-expires=1&x-signature=a";
+        assertEquals(List.of(coze), SimilarAsinImageEmbedder.downloadCandidates(coze));
+        assertEquals(List.of("https://cbu01.alicdn.com/O1CN01x.jpg"),
+                SimilarAsinImageEmbedder.downloadCandidates("https://cbu01.alicdn.com/O1CN01x.jpg"));
+    }
+
     @Test
     void buildImageRequestUsesDownloadHeadersForCozeSignedImages() {
         var req = SimilarAsinImageEmbedder.buildImageRequest(