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

.claude/settings.local.json

@@ -15,7 +15,9 @@
       "Bash(python3 *)",
       "Bash(where mypy *)",
       "Bash(pip list *)",
-      "Bash(uv run *)"
+      "Bash(uv run *)",
+      "Bash(git stash *)",
+      "Bash(dir /s /b src\\\\xmtdx)"
     ]
   }
 }