chore: 拆分app结构，将中间件、异常、子应用拆分成单独的模块

ruoyi-fastapi-backend/middlewares/cors_middleware.py

@@ -0,0 +1,18 @@
+from fastapi.middleware.cors import CORSMiddleware
+from server import app
+
+
+# 前端页面url
+origins = [
+    "http://localhost:80",
+    "http://127.0.0.1:80",
+]
+
+# 后台api允许跨域
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=origins,
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)