Enhance smoking tracking API with new features and improvements

- Added a new API endpoint `GET /api/v1/smoke/home` to consolidate core modules for the home dashboard, reducing the need for multiple requests.
- Updated the `smoke` routes to include the new home endpoint and improved user profile management with the addition of a `quit_date` field.
- Enhanced the algorithm for calculating daily targets and next smoke suggestions, ensuring accurate future time handling and user-specific recommendations.
- Improved API documentation to reflect new endpoints, response formats, and detailed field descriptions for better clarity and usability.
- Refactored user authentication handling in various handlers to streamline the process and ensure consistent error responses.

docs/smoke/ALGORITHM.md

@@ -71,6 +71,11 @@ if suggested_time in [sleep_time, wake_up_time]:
     └── 否 → 返回建议时间
 ```
 
+### 2.7 过期/未来记录兜底
+
+- 如果用户补录了“未来时间”的抽烟记录，为了避免前端出现负倒计时，服务端会把 `last_smoke_at` 限制在当前 `as_of` 时刻以内。
+- 当 `plan_date` 是“今天”且 `last_smoke_at + interval` 早于当前时间时，会根据已过去的分钟数计算需要补齐的间隔，向前跳跃若干次直到结果落在未来。这样首页和 `GET /next_smoke_time` 都能返回一个“未来的下一次建议时间”，不会出现提示已经过期的时间点。
+- 如果 `plan_date` 是将来日期（例如明天的日程），仍然按照指定日期的起床时间作为 `not_before_at`，不会使用上述补齐逻辑。
 ---
 
 ## 3. AI 增强算法
@@ -177,26 +182,22 @@ function calculateStage(startDate) {
 }
 ```
 
-### 4.3 每日目标计算
+### 4.3 每日目标计算（线性递减）
+
+以 onboarding 完成日期为起点，到 `quit_date` 线性递减到 0：
 
 ```javascript
 // utils/target.js
-function calculateDailyTarget(baseline, stage, dayInStage) {
-  if (stage === 1) {
-    return baseline
-  }
-  
-  if (stage === 2) {
-    const reduction = (dayInStage / 14) * 0.5
-    return Math.max(Math.round(baseline * (1 - reduction)), 1)
-  }
-  
-  if (stage === 3) {
-    const targetRate = 0.25 - (dayInStage / 9) * 0.25
-    return Math.max(Math.round(baseline * targetRate), 0)
-  }
-  
-  return baseline
+function calculateDailyTarget(baseline, startDate, quitDate, today) {
+  if (!baseline || !startDate || !quitDate) return baseline
+  if (today >= quitDate) return 0
+
+  const totalDays = daysBetween(startDate, quitDate)
+  if (totalDays <= 0) return baseline
+
+  const remainingDays = daysBetween(today, quitDate)
+  const target = Math.round(baseline * (remainingDays / totalDays))
+  return remainingDays > 0 ? Math.max(target, 1) : 0
 }
 ```