Fix test failures: generate unique email_inbound_token in test fixtures

UNIQUE constraint on users.email_inbound_token was violated in tests because
manual INSERT statements omitted the column. All three sites that create test
users via raw SQL now explicitly generate a unique token via secrets.token_urlsafe(16).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

tests/test_config.py

@@ -1,5 +1,7 @@
 """Tests for Settings config, specifically the database_url env var fallback."""
 
+import os
+
 from cartsnitch_api.config import Settings
 
 

tests/test_middleware/test_rate_limit.py

@@ -1,7 +1,7 @@
 """Tests for rate limiting middleware."""
 
 import time
-from unittest.mock import AsyncMock, MagicMock
+from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest