fix(core): ensure compatibility with Python < 3.12 for Buffer import

Use try/except to import Buffer from collections.abc, falling back to bytes
for older Python versions where Buffer is unavailable. This improves
backwards compatibility of ohlcv_file.py.

Author: wallneradam

src/pynecore/core/ohlcv_file.py

@@ -20,7 +20,11 @@
 import os
 import struct
 from collections import Counter
-from collections.abc import Buffer
+try:
+    from collections.abc import Buffer
+except ImportError:
+    # Python < 3.12 compatibility: Buffer was added in 3.12
+    Buffer = bytes  # type: ignore
 from datetime import datetime, time, timedelta, timezone as dt_timezone, UTC
 from io import BufferedWriter, BufferedRandom
 from math import gcd as math_gcd