零 Node 部署、超级管理员，并完善本地构建发布文档。

- FastAPI 单进程托管 frontend/dist，systemd 替代 PM2

- 超级管理员 admin、注册开关与用户管理

- README/DEPLOY/USAGE 说明：改代码须本地构建 dist 后 push，服务器 update.sh

- 提交 frontend/dist 与 build-frontend 脚本

backend/app/main.py

@@ -1,14 +1,26 @@
 from contextlib import asynccontextmanager
 from pathlib import Path
 
-from fastapi import FastAPI
+from fastapi import FastAPI, HTTPException
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import FileResponse
+from fastapi.staticfiles import StaticFiles
 
 from app.core.config import settings
 from app.core.database import Base, SessionLocal, engine
-from app.routers import auth, exams, export, students, subjects, wrong_questions
+from app.routers import admin, auth, exams, export, settings as settings_router, students, subjects, wrong_questions
 from app.services.migrate import run_migrations
-from app.services.seed import seed_subjects
+from app.services.seed import seed_admin_and_settings, seed_subjects
+
+
+def resolve_frontend_dist() -> Path | None:
+    backend_dir = Path(__file__).resolve().parent.parent
+    dist = Path(settings.FRONTEND_DIST)
+    if not dist.is_absolute():
+        dist = (backend_dir / dist).resolve()
+    if dist.is_dir() and (dist / "index.html").is_file():
+        return dist
+    return None
 
 
 @asynccontextmanager
@@ -19,6 +31,7 @@ async def lifespan(app: FastAPI):
     db = SessionLocal()
     try:
         seed_subjects(db)
+        seed_admin_and_settings(db)
     finally:
         db.close()
     yield
@@ -36,6 +49,8 @@ app.add_middleware(
 )
 
 app.include_router(auth.router, prefix="/api")
+app.include_router(settings_router.router, prefix="/api")
+app.include_router(admin.router, prefix="/api")
 app.include_router(students.router, prefix="/api")
 app.include_router(subjects.router, prefix="/api")
 app.include_router(exams.router, prefix="/api")
@@ -46,3 +61,21 @@ app.include_router(export.router, prefix="/api")
 @app.get("/api/health")
 def health():
     return {"status": "ok"}
+
+
+dist_dir = resolve_frontend_dist()
+if dist_dir is not None:
+    assets_dir = dist_dir / "assets"
+    if assets_dir.is_dir():
+        app.mount("/assets", StaticFiles(directory=assets_dir), name="assets")
+
+    @app.get("/{full_path:path}", include_in_schema=False)
+    async def serve_spa(full_path: str):
+        if full_path.startswith("api") or full_path.startswith("api/"):
+            raise HTTPException(status_code=404, detail="Not Found")
+        if full_path in ("", "index.html"):
+            return FileResponse(dist_dir / "index.html")
+        candidate = dist_dir / full_path
+        if candidate.is_file():
+            return FileResponse(candidate)
+        return FileResponse(dist_dir / "index.html")