Add server: Nightkillers, cstrike.toml

[mtsbbt157]

adding my own server

[github-actions]

Server list PR validation

Probed 1 new entry.

Gamedir	Address	Claimed	Responder	Host	Notes
cstrike	104.234.65.245:27300	48 (GoldSrc)	48 (GoldSrc)	[NIGHT KILLERS] | ZOMBIE PLAGUE | XP-LEVEL-FPS @CLANSERVERS	✅ protocol match.

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_{Probes can be flaky on the first try; the nightly publish workflow re-probes with a 48 h grace window, so a single ❌ here is not necessarily fatal. Re-push to re-run.}