refactor: 结果下载直链解析去重（11 处 → 1 处）

新增 common/service/ResultDownloadResolver，7 个模块的 resolveResultDownloadUrl
改为委托调用（appearancepatent/queryasin/withdraw/pricetrack/productrisk/
patroldelete/shopmatch）。

顺带修掉两处隐患：
- 原实现用 userId.equals(entity.getUserId())，userId 为 null 时 NPE
  （新实现用 Objects.equals）
- shopmatch 原实现在 url 为空时抛"任务不存在"，与语义不符，统一为"暂无可下载文件"

其余 4 处**刻意保留**，因为它们本就不是重复：
- shopdatacrawl：有 validateUserId + requireResultEntity + ensureResultOwner 前置校验
- deletebrand：返回 null 而非抛异常（调用方依赖该语义）
- similarasin：已分叉为返回 record ResultDownloadInfo
- brand：走的是另一套下载路径
文件名解析 resolveResultDownloadFilename 同样没收口：各模块兜底文件名策略确有差异

配套更新 3 个显式构造 Service 的测试（DelegationTest/HistoryBatchTest/
RollbackSemanticsContractTest）注入新依赖的 mock。mvn test 2795 个全绿。

backend-java/src/test/java/com/nanri/aiimage/modules/appearancepatent/service/AppearancePatentTaskServiceDelegationTest.java

@@ -98,7 +98,10 @@ class AppearancePatentTaskServiceDelegationTest {
 
     private AppearancePatentTaskService newService() {
         return new AppearancePatentTaskService(
-                localFileStorageService, null, storageProperties, fileTaskMapper, fileResultMapper,
+                localFileStorageService, null,
+                // 2026-09：结果下载解析抽到 common/ResultDownloadResolver（去 11 处重复）
+                mock(com.nanri.aiimage.common.service.ResultDownloadResolver.class),
+                storageProperties, fileTaskMapper, fileResultMapper,
                 taskScopeStateMapper, taskChunkMapper, new ObjectMapper(), llmClient, taskCacheService,
                 properties, taskFileJobService, taskProgressSnapshotService,
                 transientPayloadStorageService, transactionManager, distributedJobLockService,
@@ -109,7 +112,9 @@ class AppearancePatentTaskServiceDelegationTest {
 
     private AppearancePatentTaskService serviceWithoutTransactionManager() {
         return new AppearancePatentTaskService(
-                localFileStorageService, null, storageProperties, fileTaskMapper, fileResultMapper,
+                localFileStorageService, null,
+                mock(com.nanri.aiimage.common.service.ResultDownloadResolver.class),
+                storageProperties, fileTaskMapper, fileResultMapper,
                 taskScopeStateMapper, taskChunkMapper, new ObjectMapper(), llmClient, taskCacheService,
                 properties, taskFileJobService, taskProgressSnapshotService,
                 transientPayloadStorageService, null, distributedJobLockService,

backend-java/src/test/java/com/nanri/aiimage/modules/appearancepatent/service/AppearancePatentTaskServiceHistoryBatchTest.java

@@ -207,7 +207,10 @@ class AppearancePatentTaskServiceHistoryBatchTest {
         lenient().when(taskProgressSnapshotService.find(any(), any())).thenReturn(null);
 
         service = new AppearancePatentTaskService(
-                localFileStorageService, null, storageProperties, fileTaskMapper, fileResultMapper,
+                localFileStorageService, null,
+                // 2026-09：结果下载解析抽到 common/ResultDownloadResolver（去 11 处重复）
+                mock(com.nanri.aiimage.common.service.ResultDownloadResolver.class),
+                storageProperties, fileTaskMapper, fileResultMapper,
                 taskScopeStateMapper, taskChunkMapper, new ObjectMapper(), llmClient, taskCacheService,
                 properties, taskFileJobService, taskProgressSnapshotService,
                 transientPayloadStorageService, transactionManager, distributedJobLockService,

backend-java/src/test/java/com/nanri/aiimage/modules/task/contract/RollbackSemanticsContractTest.java

@@ -300,7 +300,10 @@ class RollbackSemanticsContractTest {
 
     private AppearancePatentTaskService appearancePatentService() {
         return new AppearancePatentTaskService(
-                localFileStorageService, ossStorageService, storageProperties, fileTaskMapper, fileResultMapper,
+                localFileStorageService, ossStorageService,
+                // 2026-09：结果下载解析抽到 common/ResultDownloadResolver（去 11 处重复）
+                mock(com.nanri.aiimage.common.service.ResultDownloadResolver.class),
+                storageProperties, fileTaskMapper, fileResultMapper,
                 taskScopeStateMapper, taskChunkMapper, objectMapper, mock(AppearancePatentLlmClient.class),
                 mock(AppearancePatentTaskCacheService.class), mock(com.nanri.aiimage.config.AppearancePatentProperties.class),
                 taskFileJobService, taskProgressSnapshotService, transientPayloadStorageService, transactionManager,