feat: add require_tenant_context and require_admin_db dependencies

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

backend/tests/test_tenant_context.py

@@ -41,3 +41,18 @@ def test_tasks_are_isolated():
     asyncio.run(run())
     assert results["a"] == "aaaaaaaa-0000-0000-0000-000000000001"
     assert results["b"] == "bbbbbbbb-0000-0000-0000-000000000002"
+
+
+@pytest.mark.asyncio
+async def test_require_tenant_context_raises_403_when_no_account():
+    from fastapi import HTTPException
+    from app.api.deps import require_tenant_context
+
+    user = MagicMock()
+    user.account_id = None
+
+    gen = require_tenant_context(current_user=user)
+    with pytest.raises(HTTPException) as exc_info:
+        await gen.__anext__()
+    assert exc_info.value.status_code == 403
+    assert "account required" in exc_info.value.detail.lower()