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

api/routes/domains.py

@@ -0,0 +1,69 @@
+"""허용 도메인 CRUD."""
+from __future__ import annotations
+
+from fastapi import APIRouter, HTTPException, Response
+from pydantic import BaseModel
+
+from config_io import load_config, save_config
+
+router = APIRouter()
+
+
+class DomainCreate(BaseModel):
+    domain: str
+    enabled: bool = True
+    note: str = ""
+
+
+class DomainPatch(BaseModel):
+    enabled: bool | None = None
+    note: str | None = None
+
+
+@router.get("/domains")
+def list_domains() -> list[dict]:
+    return load_config().get("allowed_domains", [])
+
+
+@router.post("/domains", status_code=201)
+def add_domain(body: DomainCreate) -> dict:
+    cfg = load_config()
+    domains = cfg.setdefault("allowed_domains", [])
+    name = body.domain.strip().lower()
+    if not name:
+        raise HTTPException(status_code=400, detail="domain required")
+    if any(d["domain"].lower() == name for d in domains):
+        raise HTTPException(status_code=409, detail="domain already exists")
+    entry = {"domain": name, "enabled": body.enabled, "note": body.note}
+    domains.append(entry)
+    save_config(cfg)
+    return entry
+
+
+@router.delete("/domains/{domain}", status_code=204)
+def delete_domain(domain: str) -> Response:
+    cfg = load_config()
+    name = domain.strip().lower()
+    before = len(cfg.get("allowed_domains", []))
+    cfg["allowed_domains"] = [
+        d for d in cfg.get("allowed_domains", []) if d["domain"].lower() != name
+    ]
+    if len(cfg["allowed_domains"]) == before:
+        raise HTTPException(status_code=404, detail="domain not found")
+    save_config(cfg)
+    return Response(status_code=204)
+
+
+@router.patch("/domains/{domain}")
+def patch_domain(domain: str, body: DomainPatch) -> dict:
+    cfg = load_config()
+    name = domain.strip().lower()
+    for d in cfg.get("allowed_domains", []):
+        if d["domain"].lower() == name:
+            if body.enabled is not None:
+                d["enabled"] = body.enabled
+            if body.note is not None:
+                d["note"] = body.note
+            save_config(cfg)
+            return d
+    raise HTTPException(status_code=404, detail="domain not found")