feat: merge datetime fields in DataFrame output, hide MinuteBar internal fields

- K-line: daily+ periods output 'date' only, minute periods output 'datetime'
- Transactions (tick-by-tick): combine date param + hour/minute into 'datetime'
- XdxrRecord, HistoricalFundFlow: year/month/day merged to 'date'
- MinuteBar: rename unknown_1 to _unknown_1 (hidden from DataFrame)
- MinuteBar: add datetime column computed from bar index (A-share 240-bar pattern)
- get_minute_time_data: use history endpoint only (current-day endpoint broken in pytdx too)
- Update all examples to reflect new DataFrame column names

examples/04_minute/history_minute_data.py

@@ -1,15 +1,9 @@
 """演示：获取历史某日分时数据。date 参数为 YYYYMMDD 格式的整数。"""
 
-import pandas as pd
-from easy_tdx import TdxClient, Market
+from easy_tdx import Market, TdxClient
 
 with TdxClient.from_best_host() as c:
     date = 20250110
-    bars = c.get_history_minute_time_data(Market.SH, "600000", date)
-    df = pd.DataFrame([{
-        "序号": i + 1,
-        "价格": bar.price,
-        "成交量": bar.vol,
-    } for i, bar in enumerate(bars)])
+    df = c.get_history_minute_time_data(Market.SH, "600000", date)
     print(f"浦发银行 {date} 分时数据，共 {len(df)} 条:")
-    print(df.to_string(index=False))
+    print(df.head(20).to_string(index=False))

examples/04_minute/minute_time_data.py

@@ -1,14 +1,8 @@
 """演示：获取今日分时数据（240 条）。"""
 
-import pandas as pd
-from easy_tdx import TdxClient, Market
+from easy_tdx import Market, TdxClient
 
 with TdxClient.from_best_host() as c:
-    bars = c.get_minute_time_data(Market.SH, "600000")
-    df = pd.DataFrame([{
-        "序号": i + 1,
-        "价格": bar.price,
-        "成交量": bar.vol,
-    } for i, bar in enumerate(bars)])
+    df = c.get_minute_time_data(Market.SH, "600000")
     print(f"浦发银行今日分时，共 {len(df)} 条:")
-    print(df.to_string(index=False))
+    print(df.head(20).to_string(index=False))