feat(server/devices): 设备管理 + 订阅校验中间件 (tsk_x7wrlA87orsY)

实现 server/internal/devices 模块：

- handler.go: GET /v1/me/devices 列表、DELETE /v1/me/devices/{id} 移除
  （chi 路由，挂在 /v1/me 下；JWT 中间件之后）。
- service.go: ListDevices / RegisterIfAbsent（隐式登记，按 plan.max_devices
  校验，超限返回双语 DEVICE_LIMIT_EXCEEDED 含上限数字）/ DeleteDevice（事务硬删
  + audit_log → 调 CredentialRevoker.RevokeForUser 按用户回收凭证，dp_uuid 模型）
  / SubscriptionSummary / ResolvePlan / 纯函数 resolveEffectivePlan。
- middleware.go: 订阅校验中间件，解析最高档未过期订阅注入 context；
  helpers PlanFromCtx / CheckDeviceQuota / RequirePaidTier；预留 60s Redis 缓存开关。
- store.go: devices/users/subscriptions/plans/audit_log 数据访问，按用户行锁串行化登记。
- context.go: user_id / plan 的 context key 与 helper。
- CredentialRevoker 接口（消费侧定义，避免与 nodes 循环依赖）+ NoopRevoker，
  形状对齐 #5 的 Hub.Push(RevokeCredential)，#5 落地前注入 no-op。

测试：service_test.go 15 个单测（trial→pro、过期回落 free、banned 拒绝、
最高档/同档最晚到期、UTC 严格边界、设备配额、双语限额、平台/名称归一化）全过；
devices_integration_test.go（testcontainers，build tag integration）覆盖
注册→connect 隐式登记→list→delete 全链路 + 回收断言 + 403/404。

apierr 增加 Unauthorized/Forbidden/NotFound/AccountBanned；
OpenAPI SubscriptionInfo.source 枚举补 free。

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

server/internal/devices/context.go

@@ -0,0 +1,80 @@
+package devices
+
+import (
+	"context"
+	"time"
+)
+
+// ctxKey is a private type for context keys to avoid collisions.
+type ctxKey string
+
+// CtxKeyUserID is the context key under which the authenticated user's
+// internal int64 ID is stored by the JWT auth middleware (module #2).
+//
+// It mirrors the key used by the codes module so that, once the auth
+// middleware lands, a single canonical key can be reconciled across modules.
+const CtxKeyUserID ctxKey = "user_id"
+
+// ctxKeyPlan is the context key under which the resolved subscription Plan is
+// stored by SubscriptionMiddleware.
+const ctxKeyPlan ctxKey = "plan"
+
+// WithUserID returns a copy of ctx carrying the authenticated user ID.
+// Primarily used in tests and by the auth middleware.
+func WithUserID(ctx context.Context, userID int64) context.Context {
+	return context.WithValue(ctx, CtxKeyUserID, userID)
+}
+
+// UserIDFromContext extracts the authenticated user ID from ctx.
+// ok is false when no (valid) user ID is present.
+func UserIDFromContext(ctx context.Context) (int64, bool) {
+	v, ok := ctx.Value(CtxKeyUserID).(int64)
+	if !ok || v == 0 {
+		return 0, false
+	}
+	return v, true
+}
+
+// Plan is the resolved effective subscription for a user, injected into the
+// request context by SubscriptionMiddleware and consumed by nodes (catalogue
+// filtering, connect), usage (daily caps), and the /v1/me summary.
+type Plan struct {
+	// PlanCode is one of "free", "pro", "team".
+	PlanCode string
+	// ExpiresAt is the effective subscription expiry (UTC); nil for the free
+	// fallback when the user has no active paid/trial subscription.
+	ExpiresAt *time.Time
+	// MaxDevices is the per-plan device cap (free 1 / pro 5 / team 10).
+	MaxDevices int
+	// DailyMinutes is the free-plan daily time cap in minutes; nil = unlimited.
+	DailyMinutes *int
+	// AdGate is true when the user must watch a rewarded ad to unlock daily use.
+	AdGate bool
+	// Source is the subscription source: "trial", "code", "admin", or "free"
+	// for the no-subscription fallback.
+	Source string
+}
+
+// WithPlan returns a copy of ctx carrying the resolved Plan.
+func WithPlan(ctx context.Context, p Plan) context.Context {
+	return context.WithValue(ctx, ctxKeyPlan, p)
+}
+
+// PlanFromCtx extracts the resolved Plan from ctx. ok is false when
+// SubscriptionMiddleware has not run.
+func PlanFromCtx(ctx context.Context) (Plan, bool) {
+	p, ok := ctx.Value(ctxKeyPlan).(Plan)
+	return p, ok
+}
+
+// planTier maps a plan code to a numeric tier (higher = better) for comparison.
+func planTier(code string) int {
+	switch code {
+	case "team":
+		return 3
+	case "pro":
+		return 2
+	default: // "free" or unknown
+		return 1
+	}
+}