hyperspace: raise Gradle Java source/target from 8 to 17

JDK 21 flagged source/target 8 as obsolete. The Gradle app build already
runs under JDK 17 (buildAndUpdateProduct.sh / release.yml), and AGP 8.7
permits Java 17, so bump sourceCompatibility/targetCompatibility and the
ext compat vars to 17. This covers the 4 mobile modules and the 8 java/
library subprojects compiled by Gradle; the separate Tycho/Maven OSGi
build is unaffected (its BREE pins it to Java 8 independently).

Assisted-By: Claude (claude-opus-5-5)

build.gradle

@@ -39,8 +39,8 @@ allprojects {
     version = "1.0.0-SNAPSHOT"
 
     tasks.withType(JavaCompile) {
-        sourceCompatibility = JavaVersion.VERSION_1_8
-        targetCompatibility = JavaVersion.VERSION_1_8
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
         options.encoding = "UTF-8"
     }
     defaultTasks "clean", "assemble"
@@ -54,8 +54,8 @@ ext {
     minSdk = 16
     targetSdk = 36
 
-    sourceCompatibilityVersion = JavaVersion.VERSION_1_8
-    targetCompatibilityVersion = JavaVersion.VERSION_1_8
+    sourceCompatibilityVersion = JavaVersion.VERSION_17
+    targetCompatibilityVersion = JavaVersion.VERSION_17
 
     support = "27.1.1"
     play_services_maps = "17.0.1"