fix: fresh node_uid on re-registration, remove duplicate ensure_registered call

identity_iot.py

@@ -163,9 +163,11 @@ class IdentityIoT:
                 return f.read().strip()
         except OSError:
             pass
-        raw_uid = machine.unique_id()
-        h       = uhashlib.sha256(raw_uid)
-        uid_hex = ubinascii.hexlify(h.digest()).decode()
+        # Fresh UID — hardware ID + random entropy so each new registration is unique
+        raw_uid  = machine.unique_id()
+        entropy  = bytes([urandom.getrandbits(8) for _ in range(16)])
+        h        = uhashlib.sha256(raw_uid + entropy)
+        uid_hex  = ubinascii.hexlify(h.digest()).decode()
         with open(self._F_NODEID, 'w') as f:
             f.write(uid_hex)
         return uid_hex
@@ -294,4 +296,4 @@ def _normalize_b64(s: str) -> str:
 
 
 class StateError(Exception):
-    pass
+    pass