fix(server): add Russian pricing translation guidance

Resolves N/A

Adds Russian localization guidance for the server translation pipeline so pricing copy treats “pay as you go” as usage-based billing instead of translating it literally. The override gives preferred Russian wording and explicitly rejects forms of “плакать”, which lets the l10n workflow regenerate the Russian .po file through tuistit instead of manual catalog edits.

How to test locally

• git diff --check -- server/L10N/ru.md .github/workflows/l10n.yml server/L10N.md