build(deps-dev): bump the dev-dependencies group in /backend with 4 updates

From the PR description

Bumps the dev-dependencies group in /backend with 4 updates: @stryker-mutator/core, @stryker-mutator/vitest-runner, @types/node and typescript.

Updates @stryker-mutator/core from 9.6.1 to 10.0.0

Updates @stryker-mutator/vitest-runner from 9.6.1 to 10.0.0

Updates @types/node from 22.20.1 to 26.4.0

Updates typescript from 5.9.3 to 7.0.2

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