fix: revert gradle namespaces, add release Firebase config

Reverted gradle namespace changes (io.pezkuwichain.wallet -> io.novafoundation.nova)
because they break R class references in Kotlin code.

Internal namespaces are NOT user-visible, so this is acceptable for minimum rebrand.
User-visible elements are all properly branded as Pezkuwi.

Added google-services.json for release variant.

test-shared/build.gradle

@@ -7,7 +7,7 @@ android {
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }
-    namespace 'io.pezkuwichain.wallet.test_shared'
+    namespace 'io.novafoundation.nova.test_shared'
 }