feat(invites): add revoked_at + email_sent_at to account_invites

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/tests/test_account_invite_model.py

@@ -0,0 +1,27 @@
+import pytest
+from datetime import datetime, timezone, timedelta
+from app.models.account_invite import AccountInvite
+
+
+def make_invite(**kwargs):
+    return AccountInvite(
+        account_id=kwargs.get("account_id", "00000000-0000-0000-0000-000000000001"),
+        invited_by_id=kwargs.get("invited_by_id", "00000000-0000-0000-0000-000000000002"),
+        email=kwargs.get("email", "x@y.com"),
+        code=kwargs.get("code", "ABCD1234"),
+        role=kwargs.get("role", "engineer"),
+        accepted_by_id=kwargs.get("accepted_by_id"),
+        expires_at=kwargs.get("expires_at"),
+        revoked_at=kwargs.get("revoked_at"),
+    )
+
+
+def test_invite_revoked_is_invalid():
+    invite = make_invite(revoked_at=datetime.now(timezone.utc))
+    assert invite.is_revoked is True
+    assert invite.is_valid is False
+
+
+def test_invite_unrevoked_unexpired_unused_is_valid():
+    invite = make_invite(expires_at=datetime.now(timezone.utc) + timedelta(days=7))
+    assert invite.is_valid is True