Refactor domain fronting to use configuration-based approach

How it works:
1. VPN configures NymNetworkDetails with front_hosts
2. SDK passes network_details to BaseClientBuilder via with_network_details()
3. BaseClientBuilder uses ClientBuilder::from_network() when available
4. from_network() automatically enables domain fronting if front_hosts configured

Benefits:
- Configuration-based (network_details), not object-based (cleaner)
- No breaking changes for existing clients

Changes:
- Added network_details: Option<NymNetworkDetails> to BaseClientBuilder
- Updated tests

common/http-api-client/src/lib.rs

@@ -594,10 +594,9 @@ impl ClientBuilder {
         let urls = network
             .nym_api_urls
             .as_ref()
-            .ok_or_else(|| {
-                HttpClientError::GenericRequestFailure(
-                    "No API URLs configured in network details".to_string(),
-                )
+            .ok_or_else(|| HttpClientError::InternalResponseInconsistency {
+                url: ::url::Url::parse("about:blank").unwrap(),
+                details: "No API URLs configured in network details".to_string(),
             })?
             .iter()
             .map(|api_url| {
@@ -611,8 +610,12 @@ impl ClientBuilder {
                         .iter()
                         .map(|host| format!("https://{}", host))
                         .collect();
-                    url = Url::new(api_url.url.clone(), Some(fronts))
-                        .map_err(|e| HttpClientError::GenericRequestFailure(e.to_string()))?;
+                    url = Url::new(api_url.url.clone(), Some(fronts)).map_err(|e| {
+                        HttpClientError::MalformedUrl {
+                            raw: api_url.url.clone(),
+                            source: e,
+                        }
+                    })?;
                 }
 
                 Ok(url)