feature - update gemini client to support proxy

[nihao]

• update gemini client to support proxy

    pub fn with_proxy(mut self, proxy_url: &str) -> Self {
        let proxy = reqwest::Proxy::all(proxy_url).expect("Proxy URL should be valid");
        self.http_client = reqwest::Client::builder()
            .proxy(proxy)
            .build()
            .expect("Gemini reqwest client should build");
        self
    }