feat(overlay): resolve country codes for 15 missing-country ASNs

[trick77]

Summary

Resolves country codes for all 15 entries currently in missing.json with "missing": "country". Each entry has been independently verified before inclusion.

Resolved entries

ASN	Country	Organization
AS15804	EG	The Way Out Internet Solutions
AS21942	SK	ON Semiconductor Slovakia
AS23985	HK	MGB METRO Group Buying HK Limited
AS36893	EG	Duravit Egypt
AS36911	NG	DIRECT ON PC LTD
AS36928	SL	Sierratel
AS37320	GH	NLA
AS37442	ZW	ZARNET (Zimbabwe Academic & Research Network)
AS37476	UG	Pegasus Technologies
AS37586	BI	ONATEL (Office National des Télécommunications du Burundi)
AS37703	TN	ATLAX.com
AS327933	CD	GROUPE TELECOM SPRL
AS328007	ZM	ZANACO (Zambia National Commercial Bank)
AS328144	SZ	Touch IT Investments
AS328149	KE	Web Tribe Limited

Notable distinctions

• AS21942 ON Semiconductor → SK (not US). The corporate HQ is in the United States, but this AS is operated by ON Semiconductor's Slovakia entity.
• AS37586 ONATEL → BI (not BF). There are two ONATELs in Africa — this one is the Burundi national telecom, not the Burkina Faso operator.
• AS328007 ZANACO → ZM. The org name (Zambia National Commercial Bank) is unambiguous; do not confuse the "Cairo Road" address with Egypt — Cairo Road is the main commercial street in Lusaka.

Test plan

• `python scripts/validate.py` — all 38 entries valid
• Existing 23 entries unchanged (single-line compact format preserved)
• All new entries are country-only short form
• ASN-ascending sort maintained