fix: allow dialog close labels to be customized

[codejupiter]

Summary

• Adds a closeLabel prop to Base UI and Radix DialogContent and DialogFooter, defaulting to Close for backwards compatibility.
• Uses closeLabel for the icon close button screen-reader text and optional footer close button text.
• Regenerates the v4 style registry outputs and adds a short docs note for Base and Radix dialog pages.

Why

Localized apps using the built-in close controls should not have to reimplement the default close markup just to avoid shipping hardcoded English UI or screen-reader text.

Fixes #10593.

Validation

• npx -y pnpm@9.0.6 --filter=shadcn build
• npx -y bun@latest run ./scripts/build-registry.mts from apps/v4
• npx -y pnpm@9.0.6 --filter=v4 validate:registries
• npx -y pnpm@9.0.6 --filter=v4 typecheck
• npx -y pnpm@9.0.6 --filter=v4 lint
• npx -y pnpm@9.0.6 --filter=v4 format:check
• git diff --check

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