Refine USB transport flow

- replace Android USB dependency with app-owned USB host implementation\n- restore BLE-first scanner flow with USB secondary action\n- tighten Web Serial key handling and disconnect logging\n\nTODO (follow-up):\n- review non-English localization copy for tone and consistency\n- trim remaining unused/awkward localization strings introduced during USB UI changes

android/build.gradle.kts

@@ -2,7 +2,6 @@ allprojects {
     repositories {
         google()
         mavenCentral()
-        maven(url = "https://jitpack.io")
     }
 }