feat(server): 免费版账户级分钟卡控 + 累加式看广告加时(#21 后端)

免费版此前形同虚设:ConnectNode 每次连接发固定 daily_minutes×1min TTL、
从不扣减已用,重连即崭新 10 分钟,日额度从未强制。改为账户级(全设备共享)
真卡控 + 累加式看广告加时:

- migration 000020: usage_daily 加 ad_bonus_minutes(sqlite+mysql)。
  当日额度 = plans.daily_minutes + ad_bonus_minutes;剩余 = 额度 − minutes_used。
- usage.store.AddAdBonusMinutes: 事务内累加封顶(替代布尔 MarkAdUnlocked),
  返回新总额+本次实际加时;GetDay/GetUsageRange 补读 ad_bonus_minutes。
- usage.service.UnlockAd: verify+nonce 后 +adBonusPerAd(10) 封顶 adDailyBonusCeiling(120),
  返回 granted+remaining;TodaySummary 加 MinutesCap/AdBonusMinutes。
- usage.ads DevVerifier: 放行式占位校验(nonce 防重放仍生效),接真 AdMob 前
  让看广告加时流程可端到端跑通;main.go 按 ADS_DEV_MODE/默认装配。
- ads/unlock: 204 → 200 返回 {granted_minutes, minutes_remaining}。
- ConnectNode 免费门: 读 AccountDayMinutes(used,bonus) → remaining≤0 拒 QUOTA_EXHAUSTED,
  否则 TTL=remaining(凭证到点硬切断兜底)。nodes.store 加 AccountDayMinutes。
- /me: 补 ad_bonus_minutes,quota_today_min 分母改 daily+bonus,加 quota_cap_min。
- quota.CheckFreeConnect 同步累加语义(免费基础 10 分钟不再需先看广告)。
- openapi + 契约/迁移版本/集成测试同步;新增 SQLite AddAdBonusMinutes 单测。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/internal/httpapi/account.go

@@ -31,7 +31,8 @@ type meResponse struct {
 	// Web user-center fields.
 	DevicesUsed   int       `json:"devices_used"`
 	DevicesMax    int       `json:"devices_max"`
-	QuotaTodayMin *int      `json:"quota_today_min"` // null = unlimited (pro/team)
+	QuotaTodayMin *int      `json:"quota_today_min"` // 剩余分钟; null = unlimited (pro/team)
+	QuotaCapMin   *int      `json:"quota_cap_min"`   // 当日额度 = daily + 看广告 bonus; null = unlimited
 	DataTodayGB   float64   `json:"data_today_gb"`
 	WeeklyGB      []float64 `json:"weekly_gb"` // last 7 days, oldest→newest
 	TOTPEnabled   bool      `json:"totp_enabled"`
@@ -99,11 +100,12 @@ func (a *AccountAPI) GetMe(w http.ResponseWriter, r *http.Request) {
 	// 日期在 Go 端算好传 ?,不用 MySQL 专属 UTC_DATE()(否则 SQLite 报错→恒 0)。
 	var todayBytes uint64
 	var todayMinutes int
+	var todayAdBonus int
 	today := time.Now().UTC().Format("2006-01-02")
 	_ = a.db.QueryRowContext(ctx, `
-		SELECT COALESCE(bytes_up, 0) + COALESCE(bytes_down, 0), COALESCE(minutes_used, 0)
+		SELECT COALESCE(bytes_up, 0) + COALESCE(bytes_down, 0), COALESCE(minutes_used, 0), COALESCE(ad_bonus_minutes, 0)
 		FROM usage_daily WHERE user_id = ? AND date = ?
-	`, uid, today).Scan(&todayBytes, &todayMinutes)
+	`, uid, today).Scan(&todayBytes, &todayMinutes, &todayAdBonus)
 
 	resp := meResponse{
 		UUID:        uuid,
@@ -121,11 +123,14 @@ func (a *AccountAPI) GetMe(w http.ResponseWriter, r *http.Request) {
 		resp.ExpiresAt = &s
 	}
 	// quota_today_min: null when the plan is unlimited, else remaining minutes.
+	// 额度 = plan.daily_minutes + 当日看广告累加的 ad_bonus_minutes(账户共享)。
 	if dailyMinutes.Valid {
-		rem := int(dailyMinutes.Int64) - todayMinutes
+		cap := int(dailyMinutes.Int64) + todayAdBonus
+		rem := cap - todayMinutes
 		if rem < 0 {
 			rem = 0
 		}
+		resp.QuotaCapMin = &cap
 		resp.QuotaTodayMin = &rem
 	}