Fix speed field name in index_owntrack.html

- Change loc.velocity to loc.speed to match JSON response

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

index_owntrack.html

@@ -109,8 +109,8 @@
                     }
 
                     // Geschwindigkeit hinzufügen, falls vorhanden
-                    if (loc.velocity !== undefined && loc.velocity !== null) {
+                    if (loc.speed !== undefined && loc.speed !== null) {
-                        const speedKmh = (loc.velocity * 3.6).toFixed(1); // m/s zu km/h
+                        const speedKmh = (loc.speed * 3.6).toFixed(1); // m/s zu km/h
                         popupContent += `<br>🚗 Speed: ${speedKmh} km/h`;
                     }