feat(gemini): use model instead of modelName

src/lib/providers/gemini.ts

@@ -75,7 +75,7 @@ export const loadGeminiChatModels = async () => {
         displayName: model.displayName,
         model: new ChatGoogleGenerativeAI({
           apiKey: geminiApiKey,
-          modelName: model.key,
+          model: model.key,
           temperature: 0.7,
         }) as unknown as BaseChatModel,
       };