feat(scan): add buffer protocol support for zero-copy scanning

[darvid]

Summary

• Update Database_scan to accept any buffer protocol object (memoryview, bytearray, etc.) instead of requiring exact bytes objects
• Update Stream_scan to use y* format specifier for buffer protocol support
• Add tests for memoryview and bytearray scanning in block, stream, and chimera modes

This allows users to scan data without copying when they already have it in a buffer:

db.scan(memoryview(b"foobar"), match_event_handler=callback)
db.scan(bytearray(b"foobar"), match_event_handler=callback)

with db.stream(match_event_handler=callback) as stream:
    stream.scan(memoryview(b"foo"))

Closes #250

Test plan

• test_chimera_scan_memoryview - chimera mode with memoryview
• test_block_scan_memoryview - block mode with memoryview
• test_block_scan_bytearray - block mode with bytearray
• test_stream_scan_memoryview - stream mode with memoryview
• test_stream_scan_bytearray - stream mode with bytearray
• All existing tests still pass (32/32)