perf(queue): 按策略动态扩缩异步 Worker

将 River 执行容量按平台模型与用户组的有效并发策略动态调整，并为长任务续租、并发租约原子抢占和限流退避补充保护。\n\n统一平台模型限流继承语义，兼容历史 platformLimits/modelLimits，并为三个迁移图像模型建立独立并发租约。补充管理端显式继承/覆盖配置、指标、单元测试及隔离 PostgreSQL 验收。\n\n验证：go test ./... -count=1；pnpm lint；pnpm test；pnpm build；隔离 PostgreSQL 并发原子性/续租测试；128 任务与三分钟长任务动态 Worker 验收。

apps/api/internal/runner/limits.go

@@ -74,7 +74,7 @@ func (s *Service) rateLimitReservations(ctx context.Context, user *auth.User, ca
 				"groupKey": group.GroupKey,
 				"name":     group.Name,
 			},
-			group.RateLimitPolicy,
+			store.NormalizeRateLimitPolicy(group.RateLimitPolicy),
 			body,
 		)...)
 	}
@@ -82,27 +82,15 @@ func (s *Service) rateLimitReservations(ctx context.Context, user *auth.User, ca
 }
 
 func effectiveRateLimitPolicy(candidate store.RuntimeModelCandidate) map[string]any {
-	policy := candidate.PlatformRateLimitPolicy
-	if strings.TrimSpace(candidate.RuntimePolicySetID) != "" {
-		policy = candidate.RuntimeRateLimitPolicy
-	} else if hasRules(candidate.RuntimeRateLimitPolicy) {
-		policy = mergeMap(policy, candidate.RuntimeRateLimitPolicy)
-	}
-	if _, hasOverride := candidate.RuntimePolicyOverride["rateLimitPolicy"]; hasOverride {
-		nested, _ := candidate.RuntimePolicyOverride["rateLimitPolicy"].(map[string]any)
-		if len(nested) == 0 {
-			policy = nil
-		} else {
-			policy = mergeMap(policy, nested)
-		}
-	}
-	if hasRules(candidate.ModelRateLimitPolicy) {
-		policy = mergeMap(policy, candidate.ModelRateLimitPolicy)
-	}
-	if hasRules(policy) {
-		return policy
-	}
-	return nil
+	return store.EffectiveRateLimitPolicy(store.EffectiveRateLimitPolicyInput{
+		BasePolicy:            candidate.BaseRateLimitPolicy,
+		PlatformPolicy:        candidate.PlatformRateLimitPolicy,
+		RuntimePolicy:         candidate.RuntimeRateLimitPolicy,
+		RuntimePolicyExplicit: candidate.RuntimePolicyExplicit,
+		RuntimePolicyOverride: candidate.RateLimitRuntimeOverride,
+		ModelPolicy:           candidate.ModelRateLimitPolicy,
+		ModelPolicyMode:       candidate.ModelRateLimitPolicyMode,
+	})
 }
 
 func effectiveRetryPolicy(candidate store.RuntimeModelCandidate) map[string]any {