Fix Google Drive backup OAuth configuration

- Add new debug keystore with unique SHA-1 fingerprint
- Update google-services.json with proper OAuth clients
- Configure debug build to use new keystore
- Both Android OAuth client (type 1) and Web client (type 3) now present

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -15,6 +15,7 @@ app/*.apk
 
 *.jks
 !develop_key.jks
+!app/pezkuwi_debug.jks
 .java-version
 
 # ignore database schemas