feat(localization): translate cash shop administration into Chinese

[Qinjianbo]

Adds Simplified Chinese translations for the cash shop catalog, balance and purchase-history screens, related model captions, and the cash shop configuration update plugin.

Only three zh-CN.resx files change (64 existing resource keys). Neutral resources, behavior, and package names are unchanged. Package-name localization is tracked separately in #1250.

Validation: 40 Web localization tests passed on current master (dotnet test tests/MUnique.OpenMU.Web.Tests -c Release -p:ci=true --filter FullyQualifiedName~Localization), including resource/placeholder checks. These captions were also checked in the locally deployed admin panel.

[sven-n]

Review: looks good.

Verified locally (head 453c801, merged with current master together with #1252):

• src/Startup builds with 0 errors.
• MUnique.OpenMU.Web.Tests: 279/279 pass, including the localization and placeholder checks.
• MUnique.OpenMU.Tests: 1898/1898 pass.
• All three zh-CN.resx files are well-formed XML. Placeholders such as {0} in CashShopCoinsOf are kept.

Notes:

• The change only adds translations to existing keys, with no neutral resource or behavior changes, so the risk is low.
• Keeping WCoin (C) / WCoin (P) untranslated in the captions and explaining them in the descriptions makes sense, because those are the in-game names.

Ready to merge from my side.

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