fix: support bare proxy format (user:pass@host:port) without scheme

Normalize bare proxy strings by prepending http:// before parsing when
@ is present but :// is absent. Tests added for Python and JS.

js/src/proxy.ts

@@ -8,16 +8,28 @@ export interface ParsedProxy {
   password?: string;
 }
 
+/**
+ * Prepend http:// to schemeless proxy URLs so parsers can extract hostname.
+ * Used by geoip resolution which only needs a valid hostname, not auth fields.
+ */
+export function ensureProxyScheme(proxyUrl: string): string {
+  return proxyUrl.includes("://") ? proxyUrl : `http://${proxyUrl}`;
+}
+
 /**
  * Parse a proxy URL, extracting credentials into separate fields.
  *
  * Handles: "http://user:pass@host:port" -> { server: "http://host:port", username: "user", password: "pass" }
- * Also handles: no credentials, URL-encoded special chars, socks5://, missing port.
+ * Also handles: no credentials, URL-encoded special chars, socks5://, missing port,
+ * and bare proxy strings without a scheme (e.g. "user:pass@host:port" -> treated as http).
  */
 export function parseProxyUrl(proxy: string): ParsedProxy {
   let url: URL;
+  // Bare format: "user:pass@host:port" — new URL() throws without a scheme.
+  const normalized =
+    proxy.includes("@") && !proxy.includes("://") ? `http://${proxy}` : proxy;
   try {
-    url = new URL(proxy);
+    url = new URL(normalized);
   } catch {
     // Not a parseable URL (e.g. bare "host:port") — pass through as-is
     return { server: proxy };