Cleanup unused message embedding code

Fixup some warnings

src/parsers/location_json_parser.rs

@@ -34,6 +34,7 @@ struct LocationPoint {
 #[derive(Debug, Deserialize)]
 struct ActivityRecord {
     activity: Vec<ActivityType>,
+    #[allow(dead_code)] // Part of JSON structure, may be used in future
     timestamp_ms: Option<String>,
 }