Upgrade Spring AI to 2.0.0

[ruibaby]

Summary

• Upgrade the Spring AI BOM from 2.0.0-RC1 to 2.0.0.
• Replace the removed ChatModel.buildRequestPrompt default method with local prompt option merging for the OpenAI-compatible chat model.
• Keep tool callback validation in the request prompt path.

Testing

• ./gradlew :app:compileJava
• ./gradlew :app:test --tests "run.halo.aifoundation.provider.support.openai.OpenAiCompatibleModelsTest"
• ./gradlew :app:test
• ./gradlew test
• ./gradlew build