refactor(controller): 移除自动注入改用静态方法获取用户ID

移除StatisticsController中自动注入的UserContextUtils，改为直接调用静态方法UserContextUtils.getCurrentUserId()获取用户ID，简化代码结构并减少依赖注入

timeline-user-service/src/main/java/com/timeline/user/controller/StatisticsController.java

@@ -20,9 +20,6 @@ public class StatisticsController {
     @Autowired
     private StatisticsService statisticsService;
 
-    @Autowired
-    private UserContextUtils userContextUtils;
-
     /**
      * 获取用户统计概览
      * GET /api/v1/statistics/overview
@@ -30,7 +27,7 @@ public class StatisticsController {
      */
     @GetMapping("/overview")
     public ResponseEntity<UserStatisticsDto> getStatisticsOverview() {
-        String userId = userContextUtils.getCurrentUserId();
+        String userId = UserContextUtils.getCurrentUserId();
         log.info("获取用户统计概览: userId={}", userId);
 
         UserStatisticsDto statistics = statisticsService.getStatisticsOverview(userId);
@@ -43,7 +40,7 @@ public class StatisticsController {
      */
     @GetMapping("/uploads")
     public ResponseEntity<Object> getUploadTrends() {
-        String userId = userContextUtils.getCurrentUserId();
+        String userId = UserContextUtils.getCurrentUserId();
         log.info("获取上传趋势: userId={}", userId);
 
         Object trends = statisticsService.getUploadTrends(userId);
@@ -56,7 +53,7 @@ public class StatisticsController {
      */
     @GetMapping("/storage")
     public ResponseEntity<Object> getStorageBreakdown() {
-        String userId = userContextUtils.getCurrentUserId();
+        String userId = UserContextUtils.getCurrentUserId();
         log.info("获取存储分类: userId={}", userId);
 
         Object breakdown = statisticsService.getStorageBreakdown(userId);
@@ -69,7 +66,7 @@ public class StatisticsController {
      */
     @PostMapping("/refresh")
     public ResponseEntity<Void> refreshStatistics() {
-        String userId = userContextUtils.getCurrentUserId();
+        String userId = UserContextUtils.getCurrentUserId();
         log.info("强制刷新统计数据: userId={}", userId);
 
         statisticsService.refreshStatistics(userId);