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/store/rate_limit_status.go

@@ -143,8 +143,10 @@ func (s *Store) ListModelRateLimitStatuses(ctx context.Context) ([]ModelRateLimi
 		       p.priority, p.dynamic_priority, COALESCE(p.dynamic_priority, p.priority),
 		       m.model_name, COALESCE(NULLIF(m.provider_model_name, ''), m.model_name), COALESCE(m.model_alias, ''),
 	       m.model_type, m.display_name, m.enabled,
-	       p.rate_limit_policy, COALESCE(rp.rate_limit_policy, '{}'::jsonb), COALESCE(m.runtime_policy_set_id::text, b.runtime_policy_set_id::text, ''),
-	       COALESCE(NULLIF(m.runtime_policy_override, '{}'::jsonb), b.runtime_policy_override, '{}'::jsonb), m.rate_limit_policy,
+	       COALESCE(b.default_rate_limit_policy, '{}'::jsonb), p.rate_limit_policy,
+	       COALESCE(rp.rate_limit_policy, '{}'::jsonb),
+	       (m.runtime_policy_set_id IS NOT NULL),
+	       COALESCE(m.runtime_policy_override, '{}'::jsonb), m.rate_limit_policy, m.rate_limit_policy_mode,
 	       COALESCE(to_char(p.cooldown_until AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS.MS"Z"'), ''),
 	       COALESCE(to_char(m.cooldown_until AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS.MS"Z"'), ''),
 	       COALESCE(con.active, 0)::float8,
@@ -217,11 +219,13 @@ ORDER BY p.priority ASC, m.model_name ASC`)
 	for rows.Next() {
 		var item ModelRateLimitStatus
 		var modelTypeBytes []byte
+		var basePolicyBytes []byte
 		var platformPolicyBytes []byte
 		var runtimePolicyBytes []byte
-		var runtimePolicySetID string
+		var runtimePolicyExplicit bool
 		var runtimeOverrideBytes []byte
 		var modelPolicyBytes []byte
+		var modelPolicyMode string
 		var platformDynamicPriority sql.NullInt64
 		var platformCooldownUntil string
 		var modelCooldownUntil string
@@ -248,11 +252,13 @@ ORDER BY p.priority ASC, m.model_name ASC`)
 			&modelTypeBytes,
 			&item.DisplayName,
 			&item.Enabled,
+			&basePolicyBytes,
 			&platformPolicyBytes,
 			&runtimePolicyBytes,
-			&runtimePolicySetID,
+			&runtimePolicyExplicit,
 			&runtimeOverrideBytes,
 			&modelPolicyBytes,
+			&modelPolicyMode,
 			&platformCooldownUntil,
 			&modelCooldownUntil,
 			&concurrentCurrent,
@@ -268,13 +274,15 @@ ORDER BY p.priority ASC, m.model_name ASC`)
 		}
 		item.PlatformDynamicPriority = intPointerFromNull(platformDynamicPriority)
 		item.ModelType = decodeStringArray(modelTypeBytes)
-		policy := effectiveModelRateLimitPolicy(
-			decodeObject(platformPolicyBytes),
-			decodeObject(runtimePolicyBytes),
-			runtimePolicySetID,
-			decodeObject(runtimeOverrideBytes),
-			decodeObject(modelPolicyBytes),
-		)
+		policy := EffectiveRateLimitPolicy(EffectiveRateLimitPolicyInput{
+			BasePolicy:            decodeObject(basePolicyBytes),
+			PlatformPolicy:        decodeObject(platformPolicyBytes),
+			RuntimePolicy:         decodeObject(runtimePolicyBytes),
+			RuntimePolicyExplicit: runtimePolicyExplicit,
+			RuntimePolicyOverride: decodeObject(runtimeOverrideBytes),
+			ModelPolicy:           decodeObject(modelPolicyBytes),
+			ModelPolicyMode:       modelPolicyMode,
+		})
 		item.PlatformCooldownUntil = platformCooldownUntil
 		item.ModelCooldownUntil = modelCooldownUntil
 		item.RateLimitPolicy = policy
@@ -491,46 +499,6 @@ func platformPolicyEventFromPayload(id string, taskID string, eventType string,
 	}
 }
 
-func effectiveModelRateLimitPolicy(platformPolicy map[string]any, runtimePolicy map[string]any, runtimePolicySetID string, runtimeOverride map[string]any, modelPolicy map[string]any) map[string]any {
-	policy := platformPolicy
-	if strings.TrimSpace(runtimePolicySetID) != "" {
-		policy = runtimePolicy
-	} else if hasRateLimitRules(runtimePolicy) {
-		policy = shallowMergeMap(policy, runtimePolicy)
-	}
-	if _, hasOverride := runtimeOverride["rateLimitPolicy"]; hasOverride {
-		nested, _ := runtimeOverride["rateLimitPolicy"].(map[string]any)
-		if len(nested) == 0 {
-			policy = nil
-		} else {
-			policy = shallowMergeMap(policy, nested)
-		}
-	}
-	if hasRateLimitRules(modelPolicy) {
-		policy = shallowMergeMap(policy, modelPolicy)
-	}
-	if hasRateLimitRules(policy) {
-		return policy
-	}
-	return nil
-}
-
-func hasRateLimitRules(policy map[string]any) bool {
-	rules, _ := policy["rules"].([]any)
-	return len(rules) > 0
-}
-
-func shallowMergeMap(base map[string]any, override map[string]any) map[string]any {
-	out := map[string]any{}
-	for key, value := range base {
-		out[key] = value
-	}
-	for key, value := range override {
-		out[key] = value
-	}
-	return out
-}
-
 func rateLimitForMetric(policy map[string]any, metric string) float64 {
 	rules, _ := policy["rules"].([]any)
 	for _, rawRule := range rules {