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/controller/admin/base.go

@@ -0,0 +1,26 @@
+package admin
+
+import (
+	"github.com/assimon/luuu/controller"
+	"github.com/assimon/luuu/middleware"
+	"github.com/labstack/echo/v4"
+)
+
+// Ctrl is the singleton admin controller. Keeps parity with comm.Ctrl.
+var Ctrl = &BaseAdminController{}
+
+// BaseAdminController aggregates admin-domain handlers. Split across
+// *_controller.go files in this package; all receive methods hang off
+// this type so a single router registration is enough.
+type BaseAdminController struct {
+	controller.BaseController
+}
+
+// currentAdminUserID returns the admin user id injected by CheckAdminJWT.
+// Returns 0 if the middleware is missing (treat as auth bug upstream).
+func currentAdminUserID(ctx echo.Context) uint64 {
+	if v, ok := ctx.Get(middleware.AdminUserIDKey).(uint64); ok {
+		return v
+	}
+	return 0
+}