feat: HDF5迁移至DuckDB存储

- 新增DuckDB Storage与ThreadSafeStorage实现
- 新增db_manager模块支持增量同步策略
- DataLoader与Sync模块适配DuckDB
- 补充迁移相关文档与测试
- 修复README文档链接

src/data/api_wrappers/api_trade_cal.py

@@ -10,6 +10,10 @@ from pathlib import Path
 from src.data.client import TushareClient
 from src.data.config import get_config
 
+# Module-level flag to track if cache has been synced in this session
+_cache_synced = False
+
+
 
 # Trading calendar cache file path
 def _get_cache_path() -> Path:
@@ -51,8 +55,9 @@ def _load_from_cache() -> pd.DataFrame:
 
     try:
         with pd.HDFStore(cache_path, mode="r") as store:
-            if "trade_cal" in store.keys():
-                data = store["trade_cal"]
+            # HDF5 keys include leading slash (e.g., '/trade_cal')
+            if "/trade_cal" in store.keys():
+                data = store["/trade_cal"]
                 print(f"[trade_cal] Loaded {len(data)} records from cache")
                 return data
     except Exception as e:
@@ -77,6 +82,7 @@ def _get_cached_date_range() -> tuple[Optional[str], Optional[str]]:
 def sync_trade_cal_cache(
     start_date: str = "20180101",
     end_date: Optional[str] = None,
+    force: bool = False,
 ) -> pd.DataFrame:
     """Sync trade calendar data to local cache with incremental updates.
 
@@ -86,10 +92,17 @@ def sync_trade_cal_cache(
     Args:
         start_date: Initial start date for full sync (default: 20180101)
         end_date: End date (defaults to today)
+        force: If True, force sync even if already synced in this session
 
     Returns:
         Full trade calendar DataFrame (cached + new)
     """
+    global _cache_synced
+
+    # Skip if already synced in this session (unless forced)
+    if _cache_synced and not force:
+        return _load_from_cache()
+
     if end_date is None:
         from datetime import datetime
 
@@ -137,6 +150,8 @@ def sync_trade_cal_cache(
             combined = new_data
 
         # Save combined data to cache
+        # Mark as synced to avoid redundant syncs in this session
+        _cache_synced = True
         _save_to_cache(combined)
         return combined
     else:
@@ -153,6 +168,8 @@ def sync_trade_cal_cache(
             print("[trade_cal] No data returned")
             return data
 
+        # Mark as synced to avoid redundant syncs in this session
+        _cache_synced = True
         _save_to_cache(data)
         return data