Release signing from gitignored keystore.properties

Keystore at ~/.keystores/meddetsamme-release.jks (4096-bit RSA, 30 yr),
credentials in keystore.properties — both outside version control. A
clone without the file still builds (unsigned release) instead of
failing, so nothing breaks for CI or a fresh checkout.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -1,6 +1,8 @@
 .gradle/
 build/
 local.properties
+keystore.properties
+*.jks
 .kotlin/
 *.iml
 .idea/