fix: remove insecure empty folder cleanup logic to prevent critical data loss (#320)

- Removes clean_empty_library_items functionality that incorrectly deleted critical paths (e.g., Postgres data, Steam locks)
- Cleans up associated tests and unnecessary protection rules
- Ensures empty folders are preserved by default for safety

tests/clean_apps.bats

@@ -114,3 +114,4 @@ EOF
     [ "$status" -eq 0 ]
     [[ "$output" == "ok" ]]
 }
+