Fix device dropdown filter to show all MQTT devices

Changed strict equality (===) to loose equality (==) in loadLocations() when filtering MQTT data for device dropdown. This was preventing devices from appearing in the device selection dropdown because user_id is returned as string "0" from API.

This fix ensures both tid=10 (Joachim Pixel) and tid=11 (Huawei Smartphone) appear as selectable options in the device filter dropdown.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

index.html

@@ -380,7 +380,7 @@
                 allData = data;
 
                 // Nur MQTT-Daten für Device-Filter
-                const mqttData = data.history ? data.history.filter(loc => loc.user_id === 0) : [];
+                const mqttData = data.history ? data.history.filter(loc => loc.user_id == 0) : [];
 
                 // Update device filter dropdown
                 if (mqttData.length > 0) {