Python: OllamaChatClient does not implement service_url(), so server.address is reported as Unknown #9221

OllamaChatClient does not override BaseChatClient.service_url(), so the base default "Unknown" ends up in the server.address attribute of chat spans.

OllamaEmbeddingClient already returns its host from service_url(), and the Anthropic, Bedrock, Gemini, Mistral and OpenAI chat-completion clients all implement it. The chat client already stores the host in self.host, so it can return that.

Part of the server attribute coverage gap mentioned in #6626. I have a small fix ready.