chore: define uv version once in pre-commit config

[adamtheturtle]

Matches the pattern from literalizer: a YAML anchor .uv_version so the uv pin is declared once and referenced as *uv_version in each hook's additional_dependencies.

pre-commit validate-config may warn about an unexpected root key .uv_version; that is expected and matches literalizer.

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Note

Low Risk
Low risk config-only change that centralizes the pinned uv version; main risk is pre-commit/YAML tooling reacting differently to the new root anchor key.

Overview
Centralizes the pinned uv version in .pre-commit-config.yaml by introducing a root YAML anchor (.uv_version: &uv_version uv==0.9.5).

Updates every local hook to use additional_dependencies: [*uv_version] instead of repeating uv==0.9.5, reducing duplication while keeping hook behavior the same.

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