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.

common/build.gradle

@@ -71,7 +71,7 @@ android {
         }
     }
 
-    namespace 'io.pezkuwichain.wallet.common'
+    namespace 'io.novafoundation.nova.common'
 
     buildFeatures {
         viewBinding true