Combined flash + key exchange flow with version check and USB permission persistence

- Firmware: add VERSION? command returning BUILD_NR for version check
- Android: flash button checks firmware version first, skips flash if current
- After flash: auto key exchange via reboot detection (expectingReboot flag)
- device_filter.xml + intent-filter: USB permission 'always allow' checkbox
- singleTop + onNewIntent prevents unwanted SettingsActivity launch on USB connect
- platformio.ini: upload_port updated to /dev/ttyACM1

android/app/src/main/res/values/strings.xml

@@ -57,7 +57,9 @@
     <string name="msg_reading_key">Sleutel uitlezen…</string>
     <string name="msg_flash_download_mode">Sluit de ESP aan via USB om te flashen.</string>
     <string name="msg_initializing">Initialiseren…</string>
-    <string name="msg_flash_complete">Firmware geflashed!\n\nDe ESP herstart automatisch. Sleutels blijven behouden in NVS.</string>
+    <string name="msg_checking_version">Firmware versie controleren…</string>
+    <string name="msg_env_waiting_reboot">Wachten op ESP herstart…</string>
+    <string name="msg_flash_complete">Firmware geflashed!\n\nSleutels worden nu uitgelezen…</string>
     <string name="button_close">Sluiten</string>
     <string name="button_cancel">Annuleren</string>
 

android/app/src/main/res/xml/device_filter.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <usb-device vendor-id="12346" product-id="4097" />
+</resources>