fix: use mtime (not birthtime) for UUID birthday — rsync preserves mtime across systems

src/watcher/watcher.rs

@@ -93,7 +93,7 @@ pub async fn pre_process_file(file_path: &str) -> Option<String> {
         .unwrap_or_else(|_| "/Users/accusys/momentry/output_dev".to_string());
 
     let birthday = std::fs::metadata(&path).ok()
-        .and_then(|m| m.created().ok())
+        .and_then(|m| m.modified().ok())
         .map(|t| {
             let secs = t.duration_since(std::time::UNIX_EPOCH).unwrap_or_default().as_secs();
             chrono::DateTime::from_timestamp(secs as i64, 0)