feat(invites): wire EmailService.send_account_invite_email into create handler

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

backend/tests/test_account_invite_extensions.py

@@ -0,0 +1,54 @@
+import pytest
+from unittest.mock import AsyncMock, patch
+from sqlalchemy import select
+from app.models.account_invite import AccountInvite
+
+
+@pytest.mark.asyncio
+async def test_create_invite_sends_email_and_stamps_email_sent_at(
+    client, test_db, test_user, auth_headers
+):
+    """Regression: today's create_invite does NOT send email. After this task, it MUST."""
+    with patch(
+        "app.core.email.EmailService.send_account_invite_email",
+        new_callable=AsyncMock, return_value=True,
+    ) as mock_send:
+        response = await client.post(
+            "/api/v1/accounts/me/invites",
+            json={"email": "teammate@example.com", "role": "engineer"},
+            headers=auth_headers,
+        )
+    assert response.status_code == 201, response.json()
+    mock_send.assert_called_once()
+    kwargs = mock_send.call_args.kwargs
+    assert kwargs["to_email"] == "teammate@example.com"
+    assert kwargs["role"] == "engineer"
+    assert kwargs["code"]
+
+    invite = (await test_db.execute(
+        select(AccountInvite).where(AccountInvite.email == "teammate@example.com")
+    )).scalar_one()
+    assert invite.email_sent_at is not None
+
+
+@pytest.mark.asyncio
+async def test_create_invite_email_failure_still_creates_row(
+    client, test_db, test_user, auth_headers
+):
+    """When EmailService returns False, the invite row is still created but
+    email_sent_at remains NULL."""
+    with patch(
+        "app.core.email.EmailService.send_account_invite_email",
+        new_callable=AsyncMock, return_value=False,
+    ):
+        response = await client.post(
+            "/api/v1/accounts/me/invites",
+            json={"email": "fail-mail@example.com", "role": "engineer"},
+            headers=auth_headers,
+        )
+    assert response.status_code == 201
+
+    invite = (await test_db.execute(
+        select(AccountInvite).where(AccountInvite.email == "fail-mail@example.com")
+    )).scalar_one()
+    assert invite.email_sent_at is None