全面修改图表绘制方法，确保中文字符正常输出。优化程序性能，修复_analyze_group_genre_preference函数中存在严重的逻辑错误。

analysis_results/analysis_summary.json

@@ -1,28 +1,28 @@
 {
-    "Data Overview": {
-        "Number of Users": 6040,
-        "Number of Movies": 3883,
-        "Original Ratings Count": 1000209,
-        "Filled Ratings Count": 22384240
+    "数据概览": {
+        "用户数量": 6040,
+        "电影数量": 3883,
+        "原始评分数量": 1000209,
+        "填补后评分数量": 22384240
     },
-    "User Analysis": {
-        "Gender Distribution": {
+    "用户分析": {
+        "性别分布": {
             "M": 4331,
             "F": 1709
         },
-        "Age Distribution": {
+        "年龄分布": {
             "25-34": 2096,
             "35-44": 1193,
             "18-24": 1103,
             "45-49": 550,
             "50-55": 496,
-            "56+": 380,
-            "Under 18": 222
+            "56岁以上": 380,
+            "18岁以下": 222
         }
     },
-    "Rating Analysis": {
-        "Average Rating": 3.58,
-        "Rating Distribution": {
+    "评分分析": {
+        "平均评分": 3.58,
+        "评分分布": {
             "1": 56174,
             "2": 107557,
             "3": 261197,