Add admin UI

internal/admin/routes.go

@@ -0,0 +1,17 @@
+package admin
+
+import (
+	"net/http"
+)
+
+// RegisterRoutes wires the admin HTTP handlers onto the provided mux.
+func (s *AdminServer) RegisterRoutes(mux *http.ServeMux) {
+	// API endpoints
+	mux.HandleFunc("/admin/api/v1/system/info", s.handleSystemInfo)
+	mux.HandleFunc("/admin/api/v1/system/health", s.handleSystemHealth)
+	mux.HandleFunc("/admin/api/v1/config", s.handleConfig)
+	mux.HandleFunc("/admin/api/v1/providers", s.handleProviders)
+
+	// Serve frontend SPA
+	mux.Handle("/admin/", http.StripPrefix("/admin", s.serveSPA()))
+}