Add traffic count utility scripts

[keilogic]

Summary

• add external_hosts to count outbound external destination hosts from live traffic or a pcap
• add protocol_counts to summarize IP/transport protocol usage from the packet stream
• share the counting logic in chains.utils.traffic_counts and cover it with focused tests

Fixes #3.

Verification

• py -m py_compile setup.py chains\utils\traffic_counts.py chains\utils\traffic_counts_test.py scripts\external_hosts scripts\protocol_counts
• py -m pytest chains\utils\traffic_counts_test.py -q
• py -m flake8 setup.py chains\utils\traffic_counts.py chains\utils\traffic_counts_test.py scripts\external_hosts scripts\protocol_counts
• py setup.py --name
• git diff --check

Note: running the scripts against the bundled pcaps was not possible in this local Windows/Python 3.13 environment because the current base branch imports native capture dependencies (pcapy / netifaces) that are not installed here. The new counting helper tests avoid those native dependencies.