Handle missing monstr dependency

src/nostr/event_handler.py

@@ -3,7 +3,16 @@
 import time
 import logging
 import traceback
-from monstr.event.event import Event
+
+try:
+    from monstr.event.event import Event
+except ImportError:  # pragma: no cover - optional dependency
+
+    class Event:  # minimal placeholder for type hints when monstr is absent
+        id: str
+        created_at: int
+        content: str
+
 
 # Instantiate the logger
 logger = logging.getLogger(__name__)

src/utils/key_derivation.py

@@ -23,7 +23,11 @@ import traceback
 from typing import Union
 from bip_utils import Bip39SeedGenerator
 from local_bip85.bip85 import BIP85
-from monstr.encrypt import Keys
+
+try:
+    from monstr.encrypt import Keys
+except ImportError:  # Fall back to local coincurve implementation
+    from nostr.coincurve_keys import Keys
 from cryptography.hazmat.primitives.kdf.hkdf import HKDF
 from cryptography.hazmat.primitives import hashes
 from cryptography.hazmat.backends import default_backend