[Feature Request] Add UI localization support (starting with Spanish)

Bug Description
It would be great if Claude Code supported UI localization, starting with Spanish. Right now the welcome screen and the rest of the CLI interface are English-only, with no setting (settings.json, env var, or CLI flag) to change the display language. A language/locale option — even starting with a few languages like Spanish — would make the tool more accessible for non-English-speaking developers.

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.1.214
• Feedback ID: 20b8645d-f803-451d-bfd5-cfffe269a203

Errors

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