[Bedrock] Add structured output settings toggle

[edelauna]

Which API Provider are you using?

AWS Bedrock

Which Model are you using?

Bedrock tool-use models

What happened?

Bedrock settings need a provider setting for whether Zoo Code should attempt strict structured output before falling back on unsupported models.

Steps to reproduce

1. Review the structured-output setting proposed in [ENHANCEMENT] Improve Amazon Bedrock support #125.
2. Add provider setting schema/UI wiring.
3. Add English i18n strings explaining the behavior.

Relevant API REQUEST output

N/A

Additional context

Parent issue: #124
Source PR: #125
Story point estimate: 1

Suggested PR group: PR 3 - discovery/settings UI

Acceptance criteria:

• Bedrock settings expose a strict structured-output toggle.
• The setting persists through provider settings.
• Default behavior is explicit and covered when the setting is unset.
• Webview tests verify field wiring through cached state.

This issue should only expose the setting; runtime fallback behavior belongs to the runtime issue.