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/config.py

@@ -0,0 +1,42 @@
+"""전체 설정 조회/저장."""
+from __future__ import annotations
+
+from fastapi import APIRouter
+from pydantic import BaseModel, Field
+
+from config_io import load_config, save_config
+
+router = APIRouter()
+
+
+class ProxyConfig(BaseModel):
+    listen_port: int = Field(ge=1, le=65535)
+    enabled: bool
+
+
+class BackendConfig(BaseModel):
+    host: str
+    port: int = Field(ge=1, le=65535)
+
+
+class DomainEntry(BaseModel):
+    domain: str
+    enabled: bool = True
+    note: str = ""
+
+
+class FullConfig(BaseModel):
+    proxy: ProxyConfig
+    backend: BackendConfig
+    allowed_domains: list[DomainEntry]
+
+
+@router.get("/config")
+def get_config() -> dict:
+    return load_config()
+
+
+@router.put("/config")
+def put_config(body: FullConfig) -> dict:
+    save_config(body.model_dump())
+    return load_config()