feat(worker): 实现集群限流与自适应负载

保留平台模型 RPM、TPM 和并发策略语义，增加 PostgreSQL 集群级租约、饱和候选重选和多平台自动负载，避免突发任务固定等待首个平台。\n\n新增 Worker 实时负载采样、自适应 active/heavy 容量、心跳与管理端指标，并扩展本地 acceptance runner，覆盖三 Worker、同模型三平台 2/4/6 并发和 48 个带图视频突发任务。\n\n验证：go test ./...、go vet ./...、PostgreSQL 跨 Store 集成测试、gofmt、bash -n、ShellCheck 及本地集群 provider-burst 验收通过；48/48 成功，无越限、重复提交、重复计费、重复回调或终态资源泄漏。

apps/api/docs/swagger.yaml

@@ -4196,6 +4196,73 @@ definitions:
       primaryAccount:
         $ref: '#/definitions/store.GatewayWalletAccount'
     type: object
+  store.WorkerClusterRuntime:
+    properties:
+      capturedAt:
+        type: string
+      queue:
+        $ref: '#/definitions/store.WorkerQueueRuntime'
+      workers:
+        items:
+          $ref: '#/definitions/store.WorkerInstanceRuntime'
+        type: array
+    type: object
+  store.WorkerInstanceRuntime:
+    properties:
+      activeLeases:
+        type: integer
+      allocatedCapacity:
+        type: integer
+      capacityLimit:
+        type: integer
+      drainingAt:
+        type: string
+      finalizingTasks:
+        type: integer
+      hardCapacityLimit:
+        type: integer
+      heartbeatAt:
+        type: string
+      heavyCapacity:
+        type: integer
+      instanceId:
+        type: string
+      loadSampledAt:
+        type: string
+      podName:
+        type: string
+      podUid:
+        type: string
+      preparingTasks:
+        type: integer
+      pressureReason:
+        type: string
+      pressureState:
+        type: string
+      reportedActiveTasks:
+        type: integer
+      revision:
+        type: string
+      runningTasks:
+        type: integer
+      safeCapacity:
+        type: integer
+      site:
+        type: string
+      status:
+        type: string
+      waitingUpstreamTasks:
+        type: integer
+    type: object
+  store.WorkerQueueRuntime:
+    properties:
+      oldestWaitSeconds:
+        type: number
+      queued:
+        type: integer
+      running:
+        type: integer
+    type: object
 info:
   contact: {}
   description: |-
@@ -5846,6 +5913,20 @@ paths:
       summary: 更新 Runner 策略
       tags:
       - runtime
+  /api/admin/runtime/workers:
+    get:
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: OK
+          schema:
+            $ref: '#/definitions/store.WorkerClusterRuntime'
+      security:
+      - BearerAuth: []
+      summary: 获取集群 Worker 实时负载与领取容量
+      tags:
+      - acceptance
   /api/admin/system/acceptance/capacity-profiles:
     get:
       produces: