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/pages/Domains.jsx

@@ -0,0 +1,115 @@
+import { useEffect, useState } from 'react'
+import { api } from '../api.js'
+
+export default function Domains() {
+  const [domains, setDomains] = useState([])
+  const [newDomain, setNewDomain] = useState('')
+  const [newNote, setNewNote] = useState('')
+  const [error, setError] = useState(null)
+
+  async function load() {
+    try {
+      setDomains(await api.domains())
+      setError(null)
+    } catch (e) {
+      setError(e.message)
+    }
+  }
+
+  useEffect(() => {
+    load()
+  }, [])
+
+  async function add(e) {
+    e.preventDefault()
+    if (!newDomain.trim()) return
+    try {
+      await api.addDomain({ domain: newDomain.trim(), enabled: true, note: newNote })
+      setNewDomain('')
+      setNewNote('')
+      setError(null)
+      await load()
+    } catch (e) {
+      setError(e.message)
+    }
+  }
+
+  async function toggle(d) {
+    try {
+      await api.patchDomain(d.domain, { enabled: !d.enabled })
+      await load()
+    } catch (e) {
+      setError(e.message)
+    }
+  }
+
+  async function remove(d) {
+    if (!confirm(`${d.domain} 을(를) 삭제할까요?`)) return
+    try {
+      await api.deleteDomain(d.domain)
+      await load()
+    } catch (e) {
+      setError(e.message)
+    }
+  }
+
+  return (
+    <div>
+      <h1>허용 도메인</h1>
+      {error && <div className="error">{error}</div>}
+      <form onSubmit={add} className="form-row card">
+        <input
+          placeholder="mc.example.com"
+          value={newDomain}
+          onChange={(e) => setNewDomain(e.target.value)}
+        />
+        <input
+          placeholder="메모 (선택)"
+          value={newNote}
+          onChange={(e) => setNewNote(e.target.value)}
+        />
+        <button type="submit">추가</button>
+      </form>
+      <table className="table">
+        <thead>
+          <tr>
+            <th>도메인</th>
+            <th>메모</th>
+            <th style={{ width: 80 }}>활성</th>
+            <th style={{ width: 90 }}></th>
+          </tr>
+        </thead>
+        <tbody>
+          {domains.length === 0 && (
+            <tr>
+              <td colSpan={4} className="muted" style={{ textAlign: 'center', padding: 24 }}>
+                등록된 도메인이 없습니다.
+              </td>
+            </tr>
+          )}
+          {domains.map((d) => (
+            <tr key={d.domain}>
+              <td>
+                <code>{d.domain}</code>
+              </td>
+              <td>{d.note}</td>
+              <td>
+                <label className="switch">
+                  <input
+                    type="checkbox"
+                    checked={d.enabled}
+                    onChange={() => toggle(d)}
+                  />
+                  <span />
+                </label>
+              </td>
+              <td>
+                <button className="danger" onClick={() => remove(d)}>삭제</button>
+              </td>
+            </tr>
+          ))}
+        </tbody>
+      </table>
+    </div>
+  )
+}