Refactor userId handling in cigarettes and stats routes to use mongoose ObjectId for consistency; add debug logging for stats aggregation.

server/routers/smoke-tracker/cigarettes.js

@@ -1,4 +1,5 @@
 const { Router } = require('express')
+const mongoose = require('mongoose')
 
 const { getAnswer } = require('../../utils/common')
 const { CigaretteModel } = require('./model/cigarette')
@@ -27,7 +28,7 @@ router.post('/', async (req, res, next) => {
     }
 
     const item = await CigaretteModel.create({
-      userId: user.id,
+      userId: new mongoose.Types.ObjectId(user.id),
       smokedAt: date,
       note,
     })
@@ -44,7 +45,7 @@ router.get('/', async (req, res, next) => {
     const user = req.user
     const { from, to } = req.query
 
-    const filter = { userId: user.id }
+    const filter = { userId: new mongoose.Types.ObjectId(user.id) }
 
     if (from || to) {
       filter.smokedAt = {}