Fix: Translation placeholder error, improve auth detection

- Provide default empty string for error_detail placeholder
- Stop following redirects to detect auth failures properly
- Better error message when redirected to login page
- Debug logging includes username

Author: pentafive

custom_components/ntopng/config_flow.py

@@ -81,17 +81,32 @@ async def _async_test_connection(
         try:
             session = async_get_clientsession(self.hass, verify_ssl=verify_ssl)
 
-            _LOGGER.debug("Testing ntopng connection: %s", info_url)
+            _LOGGER.debug(
+                "Testing ntopng connection: %s (user: %s)", info_url, username
+            )
 
-            # Test basic connectivity
+            # Test basic connectivity (don't follow redirects - detect auth failures)
             async with session.get(
                 info_url,
                 auth=auth,
                 ssl=verify_ssl if verify_ssl else False,
                 timeout=aiohttp.ClientTimeout(total=15),
+                allow_redirects=False,
             ) as response:
                 _LOGGER.debug("ntopng info response status: %s", response.status)
 
+                # 302 redirect to login page means auth failed
+                if response.status == 302:
+                    location = response.headers.get("Location", "")
+                    if "login" in location.lower():
+                        return (
+                            False,
+                            "Authentication failed - redirected to login page. "
+                            "Check username and password.",
+                            [],
+                        )
+                    return False, f"Unexpected redirect to {location}", []
+
                 if response.status == 401:
                     return False, "Invalid username or password (401 Unauthorized)", []
 
@@ -155,7 +170,7 @@ async def async_step_user(
     ) -> ConfigFlowResult:
         """Handle the initial step - server configuration."""
         errors: dict[str, str] = {}
-        description_placeholders: dict[str, str] = {}
+        description_placeholders: dict[str, str] = {"error_detail": ""}
 
         if user_input is not None:
             url = user_input.get(CONF_URL, "").strip()
@@ -303,7 +318,7 @@ async def async_step_reconfigure(
             return self.async_abort(reason="reconfigure_failed")
 
         errors: dict[str, str] = {}
-        description_placeholders: dict[str, str] = {}
+        description_placeholders: dict[str, str] = {"error_detail": ""}
 
         if user_input is not None:
             url = user_input.get(CONF_URL, "").strip()