feat(calendar): update Event model and patch caldav.create_event with uid param

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_events_model.py

@@ -0,0 +1,26 @@
+def test_event_model_has_new_columns():
+    from fabledassistant.models.event import Event
+    cols = {c.key for c in Event.__table__.columns}
+    assert "caldav_uid" in cols
+    assert "color" in cols
+
+
+def test_event_to_dict_includes_new_fields():
+    from fabledassistant.models.event import Event
+    from datetime import datetime, timezone
+    e = Event(
+        user_id=1, uid="test-uid", title="Test",
+        start_dt=datetime(2026, 3, 25, 10, 0, tzinfo=timezone.utc),
+        caldav_uid="sync-uid", color="#6366f1",
+    )
+    d = e.to_dict()
+    assert d["caldav_uid"] == "sync-uid"
+    assert d["color"] == "#6366f1"
+
+
+def test_caldav_create_event_accepts_uid_param():
+    """caldav.create_event signature must accept an optional uid param."""
+    import inspect
+    from fabledassistant.services.caldav import create_event
+    sig = inspect.signature(create_event)
+    assert "uid" in sig.parameters