feat: add baseURL configuration for Google AI provider

[monkeyWie]

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[augmentcode]

🤖 Augment PR Summary

Summary: Adds optional baseURL configuration for the Google AI provider so requests can be routed through custom endpoints.

Changes: Updates Google provider settings/i18n to expose the new field and forces the provider settings form to remount when switching providers.

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[augmentcode]

Review completed. 1 suggestions posted.

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[augmentcode]

Because baseURL is optional, baseUrl will be undefined when unset; depending on @google/genai, explicitly passing httpOptions.baseUrl: undefined may override the SDK default endpoint and cause requests to fail. Consider only providing httpOptions when baseURL is defined (or setting a defaultValue).

Severity: medium

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