i18n(ru): add guides/data-fetching.mdx

[1t1sCooL]

Adds the Russian translation of guides/data-fetching.mdx.

• Based on the current en/guides/data-fetching.mdx from main
• Internal links point to /ru/, MDN links use the ru locale
• Code comments and example strings translated, code itself untouched
• Terminology follows i18n-guides/russian.md and existing ru pages

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ru/guides/data-fetching.mdx	Localization added, will be marked as complete.

Warnings reference

Icon	Description
🔄️	The source for this localization has been updated since the creation of this pull request, make sure all changes in the source have been applied.