server: Go 服务器（REST+WSS 网关+JWT+Argon2+配对+素材直链+任务状态机）；修复并发下线 send-on-closed-channel、下发查询 SQL 优先级、配对码原子占用、上传体积上限、JWT 默认密钥告警

server/internal/task/state.go

@@ -0,0 +1,87 @@
+package task
+
+// 任务状态
+const (
+	Draft        = "draft"
+	PendingReview = "pending_review"
+	Rejected     = "rejected"
+	Queued       = "queued"
+	Dispatched   = "dispatched"
+	Running      = "running"
+	Success      = "success"
+	Failed       = "failed"
+	Suspended    = "suspended"
+	Cancelled    = "cancelled"
+)
+
+// 动作
+type Action string
+
+const (
+	ActionSubmit   Action = "submit"
+	ActionApprove  Action = "approve"
+	ActionReject   Action = "reject"
+	ActionResubmit Action = "resubmit"
+	ActionDispatch Action = "dispatch"
+	ActionStart    Action = "start"
+	ActionSuccess  Action = "success"
+	ActionFail     Action = "fail"
+	ActionRetry    Action = "retry"
+	ActionSuspend  Action = "suspend"
+	ActionResume   Action = "resume"
+	ActionCancel   Action = "cancel"
+)
+
+// transitions 状态转移表
+var transitions = map[string]map[Action]string{
+	Draft: {
+		ActionSubmit: PendingReview,
+		ActionCancel: Cancelled,
+	},
+	PendingReview: {
+		ActionApprove: Queued,
+		ActionReject:  Rejected,
+		ActionCancel:  Cancelled,
+	},
+	Rejected: {
+		ActionResubmit: PendingReview,
+		ActionCancel:   Cancelled,
+	},
+	Queued: {
+		ActionDispatch: Dispatched,
+		ActionCancel:   Cancelled,
+	},
+	Dispatched: {
+		ActionStart:  Running,
+		ActionFail:   Failed,
+		ActionCancel: Cancelled,
+	},
+	Running: {
+		ActionSuccess: Success,
+		ActionFail:    Failed,
+		ActionSuspend: Suspended,
+		ActionCancel:  Cancelled,
+	},
+	Failed: {
+		ActionRetry:  Queued,
+		ActionCancel: Cancelled,
+	},
+	Suspended: {
+		ActionResume: Queued,
+		ActionCancel: Cancelled,
+	},
+	Success:   {},
+	Cancelled: {},
+}
+
+// Next 校验并返回下一状态；非法转移返回 ok=false
+func Next(current string, a Action) (string, bool) {
+	next, ok := transitions[current][a]
+	return next, ok
+}
+
+// Can 当前状态是否接受该动作
+func Can(current string, a Action) bool {
+	_, ok := transitions[current][a]
+	return ok
+}