Switched to native ESP32 webserver

- new status API
- webdav without crashing

firmware/lib/session/MeasurementSession.h

@@ -39,6 +39,10 @@ public:
         otherChunk->init(0, 0);
     }
 
+    uint32_t numMeasurements() const {
+        return currentChunk->getStartIndex() + currentChunk->numMeasurements();
+    }
+
     template<typename Encoder_T>
     void serialize(Encoder_T & encoder, uint32_t startIdx) const
     {