feat:(i18n): add Italian language translation

[giodegas]

Issue for this PR

Closes #28641

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds italian language.
As a nativa Italian speaker I followed instructions for deliver a full Italian translation.
Modified files:

• A packages/app/src/i18n/it.ts
• M packages/app/src/i18n/parity.test.ts
• M packages/desktop/src/renderer/i18n/index.ts
• A packages/desktop/src/renderer/i18n/it.ts
• A packages/ui/src/i18n/it.ts

How did you verify your code works?

I validated the Italian translations by running bun --check on each i18n file to verify syntax correctness, and would run the parity test suite (bun test i18n/parity.test.ts) to ensure all English keys are present with matching placeholders across all translation domains.

Screenshots / recordings

If this is a UI change, please include a screenshot or recording.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

If you do not follow this template your PR will be automatically rejected.

[github-actions]

Hey! Your PR title Feat/italian translation doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.