fix: replace deprecated utcnow() with datetime.now(timezone.utc)

app.py

@@ -4,7 +4,7 @@ try:
     import requests as _requests
 except ImportError:
     _requests = None
-from datetime import datetime, timedelta, date as date_cls
+from datetime import datetime, timedelta, date as date_cls, timezone
 from authlib.integrations.flask_client import OAuth
 
 app = Flask(__name__)
@@ -1938,7 +1938,7 @@ def calendar_ics():
         ORDER BY cb.date''').fetchall()
     conn.close()
 
-    now_str = datetime.utcnow().strftime('%Y%m%dT%H%M%SZ')
+    now_str = datetime.now(timezone.utc).strftime('%Y%m%dT%H%M%SZ')
     lines = [
         'BEGIN:VCALENDAR',
         'VERSION:2.0',
@@ -2044,8 +2044,8 @@ def _ha_sync_once():
             "SELECT id, name, ha_entity_prefix FROM printers "
             "WHERE ha_entity_prefix IS NOT NULL AND ha_entity_prefix != ''"
         ).fetchall()
-        now_iso = datetime.utcnow().isoformat()
-        window  = (datetime.utcnow() + timedelta(minutes=30)).isoformat()
+        now_iso = datetime.now(timezone.utc).replace(tzinfo=None).isoformat()
+        window  = (datetime.now(timezone.utc).replace(tzinfo=None) + timedelta(minutes=30)).isoformat()
         for p in printers:
             prefix = p['ha_entity_prefix']
             ha_status = states.get(f'sensor.{prefix}_etat_de_l_impression', 'unknown')