Initial SDP skeleton

Sandbox Deployment Platform — Go control plane + agents, NextJS dashboard,
nginx reverse proxy. Cross-compile via Docker; deploy via sshpass to
172.18.136.92 (micro) and 172.18.139.186 (gateway).

- control-plane: HTTP API, WS hub, SQLite (modernc.org/sqlite) for
  progress, .log files for log persistence
- agent-micro / agent-gateway: alpine:3.20 + bind-mounted repo,
  binary exec'd in container, no Dockerfile build step
- dashboard: NextJS static export + shadcn/ui components, single
  WebSocket hook
- docker-compose.yml: three services on alpine:latest with docker
  socket bind for agents
- scripts/: build.sh (golang:1.23-alpine cross-compile), deploy.sh,
  patch-nginx.sh (idempotent nginx splice), ssh wrappers

Runtime model: pass-through Bitbucket creds per deploy, never logged or
persisted on the agent. Control plane never touches git or docker
directly — agents do all the work locally.

dashboard/next.config.js

@@ -0,0 +1,10 @@
+/** @type {import('next').NextConfig} */
+const nextConfig = {
+  // ponytail: pure static export. nginx serves the dashboard with
+  // try_files and proxies /api/* and /ws/* to the Go control plane.
+  // The browser does plain fetch() to /api/*; no NextJS BFF layer.
+  output: 'export',
+  reactStrictMode: true,
+  images: { unoptimized: true },
+}
+module.exports = nextConfig