chore: añadir script build_dashboard.sh

Script para compilar el binario del dashboard TUI de forma independiente.
Útil para desarrollo rápido del dashboard sin recompilar todo el launcher.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dev-scripts/server/build_dashboard.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd "$(dirname "$0")/../.."
+
+echo "Building dashboard..."
+/usr/local/go/bin/go build -tags goolm -o bin/dashboard ./cmd/dashboard/
+echo "Done → bin/dashboard"