Enhance replication functionalilty

app/ui.py

@@ -703,10 +703,21 @@ def object_presign(bucket_name: str, object_key: str):
         _authorize_ui(principal, bucket_name, action, object_key=object_key)
     except IamError as exc:
         return jsonify({"error": str(exc)}), 403
-    api_base = current_app.config["API_BASE_URL"].rstrip("/")
+    
+    api_base = current_app.config.get("API_BASE_URL")
+    if not api_base:
+        api_base = "http://127.0.0.1:5000"
+    api_base = api_base.rstrip("/")
+    
     url = f"{api_base}/presign/{bucket_name}/{object_key}"
+    
+    headers = _api_headers()
+    # Forward the host so the API knows the public URL
+    headers["X-Forwarded-Host"] = request.host
+    headers["X-Forwarded-Proto"] = request.scheme
+    
     try:
-        response = requests.post(url, headers=_api_headers(), json=payload, timeout=5)
+        response = requests.post(url, headers=headers, json=payload, timeout=5)
     except requests.RequestException as exc:
         return jsonify({"error": f"API unavailable: {exc}"}), 502
     try: