android: 2.15.1 - fix startup crash: R8 stripped WorkDatabase_Impl constructor

AGP 9 strict full-mode keep rules no longer keep no-arg constructors of
-keep'd classes, so WorkManager's reflectively created Room database
lost its constructor and the app crashed in InitializationProvider.
Restore AGP 8 keep-rule semantics and keep RoomDatabase constructors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/frontends/android/app/build.gradle

@@ -45,8 +45,8 @@ android {
         minSdk = 24
         targetSdk = 36
 
-        versionCode 160
+        versionCode 161
-        versionName "2.15.0"
+        versionName "2.15.1"
 
         /* Base URL of the update storage, trailing slash included */
         buildConfigField "String", "UPDATE_BASE_URL", "\"${updateBaseUrl}\""

src/frontends/android/app/proguard-rules.txt

@@ -58,3 +58,9 @@
 # --- squash warnings for optional dependencies referenced only from XML ---
 
 -dontwarn org.bouncycastle.jsse.util.**
+
+# --- Room databases are instantiated reflectively (WorkManager's WorkDatabase_Impl) ---
+
+-keep class * extends androidx.room.RoomDatabase {
+    <init>();
+}

src/frontends/android/gradle.properties

@@ -2,3 +2,7 @@ android.enableJetifier=false
 android.nonTransitiveRClass=false
 android.useAndroidX=true
 org.gradle.jvmargs=-Xmx2048m -XX:MaxMetaspaceSize=512m -Dfile.encoding=UTF-8
+# AGP 9 strict full mode: "-keep class X" no longer keeps X's no-arg constructor,
+# which strips reflectively created classes (WorkManager's WorkDatabase_Impl
+# crashed 2.15.0 at startup). Keep the AGP 8 keep-rule semantics.
+android.r8.strictFullModeForKeepRules=false