Reworks startup graphics and timings

Reworks the graphics during the startup. Introduces a progress bar to visualize how much of the boot is completed. Also changes the the optics of the bambu, spoolman and wifi icons. They are now always displayed but they will be striked out if not working and they will start blinking. Also removes some unnessesary waits.

src/main.cpp

@@ -118,6 +118,12 @@ void loop() {
     checkWiFiConnection();
   }
 
+  // Periodic display update
+  if (intervalElapsed(currentMillis, lastWifiCheckTime, 1000)) 
+  {
+    oledShowTopRow();
+  }
+
   // Wenn Bambu auto set Spool aktiv
   if (bambuCredentials.autosend_enable && autoSetToBambuSpoolId > 0) 
   {