feat: add login secret visibility toggle

[cxymds]

Pull Request

Description

• Add an eye control to reveal or mask the key-login secret.
• Apply the same interaction to the STS secret field and reset visibility when switching login methods.
• Provide localized, accessible show/hide labels for every bundled locale.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Performance improvement
• Test improvements
• Security fix

Testing

• Unit tests added/updated
• Manual testing completed

pnpm install --frozen-lockfile
pnpm type-check
pnpm lint
pnpm format:check
pnpm test:run

All 483 tests pass. The reveal control was exercised in both key-login and STS modes at desktop and mobile viewports.

Checklist

• Code follows the project's style guidelines
• Self-review completed
• TypeScript types are properly defined
• All commit messages are in English (Conventional Commits)
• All existing tests pass
• No new dependencies added, or they are justified

Related Issues

N/A

Screenshots (if applicable)

Before

After

Additional Notes

The secret remains masked by default, and switching login methods restores the masked state.