feat(server/stats): stats-overhaul Phase2 — 每设备归因 + GB 综合配额

服务端记账从「账户」细到「每设备」(每设备独立 dp_uuid),配额单位分钟→GB
按账户综合卡控。000015_per_device_usage 迁移(mysql+sqlite 双份):devices.dp_uuid
+ usage_device_daily 表 + plans.daily_mb。handler_grpc 按 dp_uuid 回映射
(user_id,device_id) 双写账户+每设备;usage 服务/handler 暴露 /v1/usage(/devices)。
含 sqlite_per_device / usage handler 测试。

注:此迁移 prod 已 migrate up 运行、部署二进制已内嵌;本次补提交使 git 与线上一致。

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

server/internal/usage/handler.go

@@ -69,6 +69,56 @@ func (h *UsageHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	_ = json.NewEncoder(w).Encode(usageResponse{Points: points})
 }
 
+// DeviceUsageHandler serves GET /v1/usage/devices?days=N — per-device usage
+// totals for the authenticated account ("下分设备" breakdown).
+type DeviceUsageHandler struct {
+	svc *Service
+}
+
+// NewDeviceUsageHandler creates a DeviceUsageHandler.
+func NewDeviceUsageHandler(svc *Service) *DeviceUsageHandler { return &DeviceUsageHandler{svc: svc} }
+
+type deviceUsageResponse struct {
+	Devices []DeviceUsagePoint `json:"devices"`
+}
+
+// ServeHTTP implements http.Handler.
+func (h *DeviceUsageHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	userID := userIDFromContext(r)
+	if userID == 0 {
+		apierr.WriteJSON(w, http.StatusUnauthorized, &apierr.Error{
+			Code:      "UNAUTHORIZED",
+			MessageZH: "请先登录",
+			MessageEn: "Authentication required",
+		})
+		return
+	}
+
+	days := 7
+	if v := r.URL.Query().Get("days"); v != "" {
+		n, err := strconv.Atoi(v)
+		if err != nil || n < 1 || n > 90 {
+			apierr.WriteJSON(w, http.StatusBadRequest, apierr.ErrBadRequest)
+			return
+		}
+		days = n
+	}
+
+	devices, apiErr := h.svc.DeviceUsage(r.Context(), userID, days)
+	if apiErr != nil {
+		apierr.WriteJSON(w, http.StatusInternalServerError, apiErr)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(http.StatusOK)
+	_ = json.NewEncoder(w).Encode(deviceUsageResponse{Devices: devices})
+}
+
 // AdsUnlockHandler serves POST /v1/ads/unlock.
 type AdsUnlockHandler struct {
 	svc *Service