feat: implement MC domain filter proxy, API, dashboard

- proxy: asyncio TCP proxy with handshake parser, domain whitelist,
  transparent backend tunneling, SQLite logging, mtime hot reload
- api: FastAPI routes for config/domains/logs/status + restart trigger
- frontend: React + Vite NPM-style dashboard (dashboard/domains/logs/settings)
- nginx: reverse proxy for /api -> api:8000 and / -> frontend:3000
- docker-compose: full stack with shared data volume
- replace spec mc-domain-filter.md with README.md

frontend/src/api.js

@@ -0,0 +1,36 @@
+const base = '/api'
+
+async function req(path, opts = {}) {
+  const res = await fetch(base + path, {
+    headers: { 'Content-Type': 'application/json' },
+    ...opts,
+  })
+  if (!res.ok) {
+    const text = await res.text().catch(() => '')
+    throw new Error(`${res.status}: ${text || res.statusText}`)
+  }
+  if (res.status === 204) return null
+  return res.json()
+}
+
+export const api = {
+  status: () => req('/status'),
+  config: () => req('/config'),
+  putConfig: (cfg) => req('/config', { method: 'PUT', body: JSON.stringify(cfg) }),
+  domains: () => req('/domains'),
+  addDomain: (d) => req('/domains', { method: 'POST', body: JSON.stringify(d) }),
+  deleteDomain: (name) =>
+    req(`/domains/${encodeURIComponent(name)}`, { method: 'DELETE' }),
+  patchDomain: (name, body) =>
+    req(`/domains/${encodeURIComponent(name)}`, {
+      method: 'PATCH',
+      body: JSON.stringify(body),
+    }),
+  logs: (params = {}) => {
+    const q = new URLSearchParams(
+      Object.fromEntries(Object.entries(params).filter(([, v]) => v !== '' && v != null))
+    ).toString()
+    return req('/logs' + (q ? `?${q}` : ''))
+  },
+  restart: () => req('/proxy/restart', { method: 'POST' }),
+}