负载均衡重构: 子网感知选择 + 节点健康监控 + 节点注册上报API

- 新增 subnet-aware 负载策略: 根据客户端IP匹配最近/16子网节点
- 节点注册端点 (POST /api/nodes/register): 边缘节点自动注册
- 节点心跳端点 (POST /api/nodes/heartbeat): 上报CPU/RAM/带宽/连接数
- 健康汇总 (GET /api/nodes/health): 服务端汇总所有节点状态
- 配置节点新增subnet/is_origin字段
- 前端NodeManager: 实时健康状态/CPU/RAM进度条/带宽/连接数
- X-Forwarded-For/X-Real-IP透传支持客户端IP

backend/config.py

@@ -12,13 +12,20 @@ class Settings(BaseSettings):
     media_origin_hls_port: int = 8888
 
     edge_nodes: list[dict] = [
-        {"id": "edge-1", "name": "Edge Node 1", "host": "127.0.0.1",
-         "hls_port": 8889, "api_port": 9998, "weight": 100, "enabled": True},
-        {"id": "edge-2", "name": "Edge Node 2", "host": "127.0.0.1",
-         "hls_port": 8890, "api_port": 9999, "weight": 50, "enabled": True},
+        {
+            "id": "default",
+            "name": "Origin (Default)",
+            "host": "127.0.0.1",
+            "hls_port": 8888,
+            "api_port": 9997,
+            "weight": 100,
+            "enabled": True,
+            "subnet": "0.0.0.0/0",
+            "is_origin": True,
+        },
     ]
 
-    load_balance_strategy: Literal["round-robin", "weighted", "least-conn"] = "weighted"
+    load_balance_strategy: Literal["round-robin", "weighted", "least-conn", "subnet"] = "subnet"
 
     qualities: list[dict] = [
         {"label": "1080p", "width": 1920, "height": 1080, "bitrate": "5000k"},