fix: resolve merge conflict with main, fix test failures

- Merge main (pipelines feature) into branch, resolving conflicts in
  app/api/__init__.py and app/views/__init__.py by keeping all routers
  (onboarding + billing from our branch, pipelines from main)
- Fix migration 018 down_revision to depend on both 017_add_onboarding_fields
  and 017_add_pipelines (Alembic multi-head merge pattern)
- Fix test_auth_module.py: add multi_user_enabled=False to three admin-auth
  tests that call auth() directly without FastAPI DI
- Add missing SETTING_METADATA entries for allow_local_signup and all five
  Stripe config keys (fixes test_all_config_settings_have_metadata)

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

tests/test_auth_module.py

@@ -298,6 +298,11 @@ class TestAuthEndpoint:
                 mock_settings.admin_username = "admin"
                 mock_settings.admin_password = "secret123"
                 mock_settings.multi_user_enabled = False
+
+                from app.auth import auth
+
+                mock_request = MagicMock()
+                mock_form_data = {"username": "admin", "password": "wrong_password"}
                 mock_request.form = AsyncMock(return_value=mock_form_data)
                 mock_request.session = {}