feat: djapi 数据源归一化 + bug 修复 + 废弃 getDivData_AK

- 新增 djapi/api/stock/data_source.py 统一数源入口 (Tushare 单例)
- 迁移 10 个模块至统一数据源入口
- 废弃 getDivData_AK.py
- 修复 getStockDiv2.py / smoothBrush.py 等模块
- indexDatas API 参数 tscode 类型修正 (股票→指数代码)
- views.py + urls.py 接口清理
- continuation.md 状态更新

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

djapi/api/stock/smoothBrush.py

@@ -90,9 +90,9 @@ def smooth_series_brush(series: pd.Series, window_size: int = 7, threshold_facto
 
         # 决定使用哪个值填充
         if prev_valid_val is not None:
-            fill_value = next_valid_val
-        elif next_valid_val is not None:
             fill_value = prev_valid_val
+        elif next_valid_val is not None:
+            fill_value = next_valid_val
         else:
             print(f"警告: 毛刺段 {brush_indices} 无有效邻居，使用全局中位数填充。")
             fill_value = series.median()