Remove internal documentation from public repository

Author: ToastyToast25

.gitignore

@@ -55,3 +55,9 @@ CLAUDE.md
 
 # Brand change documentation
 BRAND-CHANGE.md
+
+# Internal planning and submission docs
+GOOGLE_PLAY_PREP.md
+apkautobuild.md
+flavorrelease.md
+CI-MONITORING.md