feat: add admin panel with multi-chain support and notification system

- Add full admin REST API: auth, API keys, chains, chain tokens, wallets,
  orders, RPC nodes, settings, dashboard stats, notifications
- Add JWT-based admin authentication and API key auth middleware
- Add multi-chain listeners: BSC, ETH, Polygon, Plasma, EVM WebSocket
- Add RPC node health check job with automatic failover
- Add Telegram notification channel for order events
- Add installer for first-run database initialization
- Add new DB models: admin_user, api_key, chain, chain_token,
  rpc_node, settings, notification_channel
- Add order statistics aggregation (daily/monthly/by-chain)
- Serve built admin SPA from embedded www/ assets
- Add comprehensive test coverage for all new features

src/model/mdb/rpc_node.go

@@ -0,0 +1,36 @@
+package mdb
+
+import "github.com/dromara/carbon/v2"
+
+const (
+	RpcNodeTypeHttp = "http"
+	RpcNodeTypeWs   = "ws"
+)
+
+const (
+	RpcNodeStatusUnknown = "unknown"
+	RpcNodeStatusOk      = "ok"
+	RpcNodeStatusDown    = "down"
+)
+
+// RpcNode records one RPC endpoint for a network. Clients select a node
+// by weight among rows where Enabled=true AND Status=ok. A periodic
+// task/rpc_health_job writes Status/LastLatencyMs/LastCheckedAt.
+type RpcNode struct {
+	Network       string      `gorm:"column:network;size:32;index:rpc_nodes_network_status_index,priority:1" json:"network" example:"tron"`
+	Url string `gorm:"column:url;size:512" json:"url" example:"https://api.trongrid.io"`
+	// 连接类型 http=HTTP请求 ws=WebSocket长连接
+	Type string `gorm:"column:type;size:16" json:"type" enums:"http,ws" example:"http"`
+	Weight        int         `gorm:"column:weight;default:1" json:"weight" example:"1"`
+	ApiKey        string      `gorm:"column:api_key;size:255" json:"api_key" example:"your-api-key"`
+	Enabled bool `gorm:"column:enabled;default:true" json:"enabled" example:"true"`
+	// 健康状态 unknown=未知 ok=正常 down=异常
+	Status string `gorm:"column:status;size:16;default:unknown;index:rpc_nodes_network_status_index,priority:2" json:"status" enums:"unknown,ok,down" example:"ok"`
+	LastLatencyMs int         `gorm:"column:last_latency_ms;default:-1" json:"last_latency_ms" example:"120"`
+	LastCheckedAt carbon.Time `gorm:"column:last_checked_at" json:"last_checked_at" example:"2026-04-16 12:00:00"`
+	BaseModel
+}
+
+func (r *RpcNode) TableName() string {
+	return "rpc_nodes"
+}