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/task/rpc_health_job.go

@@ -0,0 +1,97 @@
+package task
+
+import (
+	"net"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/assimon/luuu/model/data"
+	"github.com/assimon/luuu/model/mdb"
+	"github.com/assimon/luuu/util/log"
+)
+
+const rpcProbeTimeout = 5 * time.Second
+
+// RpcHealthJob periodically probes every enabled rpc_nodes row and
+// writes status/last_latency_ms. Results drive SelectRpcNode weighted
+// picking at runtime.
+type RpcHealthJob struct{}
+
+var gRpcHealthJobLock sync.Mutex
+
+func (r RpcHealthJob) Run() {
+	gRpcHealthJobLock.Lock()
+	defer gRpcHealthJobLock.Unlock()
+
+	nodes, err := data.ListRpcNodes("")
+	if err != nil {
+		log.Sugar.Errorf("[rpc-health] list nodes err=%v", err)
+		return
+	}
+	var wg sync.WaitGroup
+	for i := range nodes {
+		if !nodes[i].Enabled {
+			continue
+		}
+		wg.Add(1)
+		go func(n mdb.RpcNode) {
+			defer wg.Done()
+			status, latency := ProbeNode(n.Url)
+			if err := data.UpdateRpcNodeHealth(n.ID, status, latency); err != nil {
+				log.Sugar.Warnf("[rpc-health] update node %d err=%v", n.ID, err)
+			}
+		}(nodes[i])
+	}
+	wg.Wait()
+}
+
+// ProbeNode does a TCP dial to the RPC URL and returns (status, latencyMs).
+// Exported so the admin controller can reuse it without duplicating logic.
+func ProbeNode(rawURL string) (string, int) {
+	addr, err := ParseAddress(rawURL)
+	if err != nil {
+		return mdb.RpcNodeStatusDown, -1
+	}
+	dur, err := MeasureTCPDial(addr, rpcProbeTimeout)
+	if err != nil {
+		return mdb.RpcNodeStatusDown, -1
+	}
+	return mdb.RpcNodeStatusOk, int(dur.Milliseconds())
+}
+
+func ParseAddress(raw string) (string, error) {
+	if !strings.Contains(raw, "://") {
+		raw = "tcp://" + raw
+	}
+
+	u, err := url.Parse(raw)
+	if err != nil {
+		return "", err
+	}
+
+	host := u.Hostname()
+	port := u.Port()
+	if port == "" {
+		switch u.Scheme {
+		case "https", "wss":
+			port = "443"
+		default:
+			port = "80"
+		}
+	}
+
+	return host + ":" + port, nil
+}
+
+func MeasureTCPDial(addr string, timeout time.Duration) (time.Duration, error) {
+	start := time.Now()
+	conn, err := net.DialTimeout("tcp", addr, timeout)
+	if err != nil {
+		return 0, err
+	}
+	defer conn.Close()
+
+	return time.Since(start), nil
+}