Fix Opus RX decoding, add foreground service, last-talker display

- Decode received Opus audio: handle svxlink self-delimited framing and
  provide monotonic PTS (c2.opus.decoder discards output when PTS == 0)
- Keep connection and playback alive in background via SvxService
  (foreground service, media playback type)
- Keep screen on while app is open
- Show last talker callsign persistently instead of clearing after 4s
- Bump versionCode to 2, disable lint on release builds

app/build.gradle.kts

@@ -11,8 +11,8 @@ android {
         applicationId = "ru.ua1zbe.svxremote"
         minSdk = 26
         targetSdk = 34
-        versionCode = 1
-        versionName = "1.0"
+        versionCode = 2
+        versionName = "1.0.0"
     }
 
     buildTypes {
@@ -21,6 +21,11 @@ android {
         }
     }
 
+    lint {
+        checkReleaseBuilds = false
+        abortOnError = false
+    }
+
     compileOptions {
         sourceCompatibility = JavaVersion.VERSION_17
         targetCompatibility = JavaVersion.VERSION_17
@@ -39,8 +44,11 @@ dependencies {
 
 android {
     testOptions {
-        unitTests.all {
-            it.maxHeapSize = "256m"
+        unitTests {
+            isReturnDefaultValues = true
+            all {
+                it.maxHeapSize = "256m"
+            }
         }
     }
 }