servers: valve: add [DM]Europe server

[europedm]

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[github-actions]

Server list PR validation

✅ Ready to merge — 1 entry verified, no problems found.

Probed 1 new or changed entry.

Gamedir	Address	Change	Claimed	Responder	Host	Notes
valve	57.129.154.247:27015	new	49 (Xash)	49 (Xash)	[DM]Europe (Sentinel AntiCheat)	✅ answered on the declared protocol.

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