Add ISO15693Error exception for ISO 15693 error responses

[Copilot]

Addresses feedback on #14 regarding incomplete error handling for ISO 15693 commands. The TODO comment indicated that error responses should use a dedicated exception type instead of the generic PN5180Error.

Changes

• Added ISO15693Error exception class to constants.py that captures:

  • Command byte that triggered the error
  • Error code from the tag response
  • Full response data for debugging

• Updated send_and_receive_15693 to raise ISO15693Error instead of PN5180Error when tags return error responses

• Exported ISO15693Error from package root for public API

Usage

from pn5180_tagomatic import PN5180Proxy, ISO15693Error, ISO15693Command

reader = PN5180Proxy("/dev/ttyACM0")
try:
    data = reader.send_and_receive_15693(
        ISO15693Command.READ_SINGLE_BLOCK,
        b'\x05'  # block number
    )
except ISO15693Error as e:
    print(f"Command 0x{e.command:02X} failed with code 0x{e.error_code:02X}")
    print(f"Raw response: {e.response_data.hex()}")

Users can now catch ISO 15693-specific errors separately from general PN5180 communication failures and access the complete error response data.

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