feat: add background music support and static files mount

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

main.py

@@ -1,4 +1,5 @@
 from fastapi import FastAPI, WebSocket, WebSocketDisconnect, Request
+from fastapi.staticfiles import StaticFiles
 from fastapi.templating import Jinja2Templates
 from fastapi.responses import HTMLResponse, JSONResponse
 import json, time, random, sqlite3, os
@@ -6,6 +7,7 @@ from datetime import datetime
 
 DB_PATH = os.environ.get("DB_PATH", "/data/rr.db")
 app = FastAPI()
+app.mount("/static", StaticFiles(directory="static"), name="static")
 templates = Jinja2Templates(directory="templates")
 
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