fix(jade): improve PIN server handshake reliability

- Handle multiple fallback URLs when primary PIN server fails
- Add proper Accept header to PIN server requests
- Provide detailed error messages for debugging handshake issues
- Match Python jadepy library behavior more closely

This should resolve handshake failures when the first PIN server
URL is unavailable or returns errors.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: edouardparis

src/jade/pinserver.rs

@@ -21,18 +21,46 @@ impl PinServerClient {
     where
         D: serde::de::DeserializeOwned,
     {
-        let url = match &req.urls {
-            api::PinServerUrls::Array(urls) => urls.first().ok_or(Error::NoUrlProvided)?,
-            api::PinServerUrls::Object { url, .. } => url,
+        let urls = match &req.urls {
+            api::PinServerUrls::Array(urls) => {
+                if urls.is_empty() {
+                    return Err(Error::NoUrlProvided);
+                }
+                urls.clone()
+            }
+            api::PinServerUrls::Object { url, .. } => vec![url.clone()],
         };
 
-        let res = self.client.post(url).json(&req.data).send().await?;
+        let mut last_error = None;
+        
+        for url in urls {
+            let res = self
+                .client
+                .post(&url)
+                .header("Accept", &req.accept)
+                .json(&req.data)
+                .send()
+                .await;
 
-        if res.status().is_success() {
-            res.json().await.map_err(Error::from)
-        } else {
-            Err(Error::Server(format!("{:?}", res)))
+            match res {
+                Ok(response) if response.status().is_success() => {
+                    return response.json().await.map_err(Error::from);
+                }
+                Ok(response) => {
+                    last_error = Some(Error::Server(format!(
+                        "HTTP {} from {}: {:?}", 
+                        response.status(), 
+                        url, 
+                        response
+                    )));
+                }
+                Err(e) => {
+                    last_error = Some(Error::Client(e));
+                }
+            }
         }
+
+        Err(last_error.unwrap_or(Error::NoUrlProvided))
     }
 }