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>

api/src/cartsnitch_api/schemas.py

@@ -1,7 +1,6 @@
 """Pydantic v2 request/response schemas for all API endpoints."""
 
 from datetime import datetime
-from uuid import UUID
 
 from pydantic import BaseModel, EmailStr, Field
 
@@ -16,7 +15,7 @@ class UpdateUserRequest(BaseModel):
 
 
 class UserResponse(BaseModel):
-    id: UUID
+    id: str
     email: str
     display_name: str
     created_at: datetime
@@ -265,13 +264,6 @@ class ErrorResponse(BaseModel):
     code: str | None = None
 
 
-# ---------- Email-In ----------
-
-class EmailInAddressResponse(BaseModel):
-    email_address: str
-    instructions: str
-
-
 # Rebuild forward refs
 ProductDetailResponse.model_rebuild()
 PriceTrendResponse.model_rebuild()