Fix user_id type comparison in location filter

Changed strict equality (===) to loose equality (==) in applyFilters() to handle user_id being returned as string "0" from API instead of number 0. This was preventing MQTT location data from being displayed on the map.

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Co-Authored-By: Claude <noreply@anthropic.com>

index.html

@@ -263,8 +263,8 @@
         function applyFilters() {
             if (!allData || !allData.history) return;
 
-            // Nur MQTT-Daten (user_id = 0)
-            let filteredData = allData.history.filter(loc => loc.user_id === 0);
+            // Nur MQTT-Daten (user_id = 0 oder "0")
+            let filteredData = allData.history.filter(loc => loc.user_id == 0);
 
             // Apply filters in sequence
             filteredData = filterByDevice(filteredData);