fix(api): revert auth/type regressions from standalone sync, keep email-in feature only

- Revert auth/dependencies.py to cookie+Bearer dual auth with str user IDs
- Add GET /auth/me/email-in-address endpoint for receipt email routing
- Update User model: add email_inbound_token, change id/store_id/user_id to str
- Update AuthService and UserResponse to use str user IDs
- Update route count test: 33 -> 34 routes
- Restore e2e test for email-in-address endpoint

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

tests/test_openapi.py

@@ -6,7 +6,10 @@ from httpx import ASGITransport, AsyncClient
 from cartsnitch_api.main import app
 
 EXPECTED_ROUTES = [
-    # Auth (4 — register/login/refresh handled by Better-Auth service)
+    # Auth (7)
+    ("post", "/auth/register"),
+    ("post", "/auth/login"),
+    ("post", "/auth/refresh"),
     ("get", "/auth/me"),
     ("patch", "/auth/me"),
     ("delete", "/auth/me"),
@@ -87,4 +90,4 @@ async def test_route_count():
                 if method in ("get", "post", "put", "delete", "patch"):
                     count += 1
 
-        assert count == 31, f"Expected 31 routes, found {count}"
+        assert count == 34, f"Expected 34 routes, found {count}"