feat: add toggle to show unvalidated models in model selector (#413)

* feat: add toggle to show unvalidated models in model selector

Add a toggle switch in the model configuration dialog to allow users to
display models that haven't been validated. This helps users who work with
model providers that have disabled their verification endpoints.

Changes:
- Add showUnvalidatedModels field to MultiModelConfig type
- Add setShowUnvalidatedModels method to useModelConfig hook
- Add Switch toggle in model-config-dialog footer
- Update model-selector to filter based on showUnvalidatedModels setting
- Add warning icon for unvalidated models in the selector
- Add i18n translations for en/zh/ja

Closes #410

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: wrap AlertTriangle in span for title attribute

The AlertTriangle icon from lucide-react doesn't support the title prop directly.
Wrapped it in a span element to properly display the tooltip.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

lib/i18n/dictionaries/zh.json

@@ -243,6 +243,9 @@
         "default": "默认",
         "serverDefault": "服务器默认",
         "configureModels": "配置模型...",
-        "onlyVerifiedShown": "仅显示已验证的模型"
+        "onlyVerifiedShown": "仅显示已验证的模型",
+        "showUnvalidatedModels": "显示未验证的模型",
+        "allModelsShown": "显示所有模型（包括未验证的）",
+        "unvalidatedModelWarning": "此模型尚未验证"
     }
 }