added delay before announce for TCP readiness

The announce was firing before the TCP transport connection was fully
established, causing Docker instances to never announce over the mesh.

app.py

@@ -93,6 +93,8 @@ def main():
         allow=RNS.Destination.ALLOW_ALL,
     )
 
+    # Brief delay to ensure all interfaces (especially TCP) are fully ready
+    time.sleep(2)
     destination.announce()
     set_setting("dest_hash", destination.hash.hex())
     start_gateway(reticulum)