frontend/android: push min sdk version to 24 (Android 7)

Some of the calls used in the code (e.g. those that fetch the native
locale of the device) require sdk versions 24.

Author: Beerosagos

backend/mobileserver/Makefile

@@ -4,7 +4,7 @@ include ../../version.mk.inc
 # Set -glflags to fix the vendor issue with gomobile, see: https://github.com/golang/go/issues/67927#issuecomment-2241523694
 build-android:
 	# androidapi version should match minSdkVersion in frontends/android/BitBoxApp/app/build.gradle
-	ANDROID_HOME=${ANDROID_SDK_ROOT} gomobile bind -x -a -glflags="-mod=readonly" -ldflags="-s -w $(GO_VERSION_LDFLAGS)" -trimpath -target android -androidapi 21 .
+	ANDROID_HOME=${ANDROID_SDK_ROOT} gomobile bind -x -a -glflags="-mod=readonly" -ldflags="-s -w $(GO_VERSION_LDFLAGS)" -trimpath -target android -androidapi 24 .
 build-ios:
 	gomobile bind -x -a -glflags="-mod=readonly" -tags="timetzdata" -trimpath -ldflags="-s -w $(GO_VERSION_LDFLAGS)" -target ios,iossimulator .
 clean:

frontends/android/BitBoxApp/app/build.gradle

@@ -13,9 +13,9 @@ android {
     ndkVersion "28.2.13676358"
     defaultConfig {
         applicationId "ch.shiftcrypto.bitboxapp"
+        minSdk 24
         // minSdkVersion should match the `-androidapi` gomobile bind flag
         // in backend/mobileserver/Makefile
-        minSdkVersion 21
         targetSdkVersion 35
         versionCode 66
         versionName "${appVersion}"