重构项目结构，移除Assignment相关功能，优化Submission模块

TechHelper.Server/appsettings.json

@@ -6,16 +6,16 @@
     }
   },
   "ConnectionStrings": {
-    "XSDB": "Server=mysql.eazygame.cn;Port=13002;Database=test1;User=root;Password=wx1998WX"
+    "XSDB": "Server=mysql.eazygame.cn;Port=13002;Database=test3;User=root;Password=wx1998WX"
   },
   "JWTSettings": {
     "securityKey": "MxcxQHVYVDQ0U3lqWkIwdjZlSGx4eFp6YnFpUGxodmc5Y3hPZk5vWm9MZEg2Y0I=",
     "validIssuer": "CodeMazeAPI",
-    "validAudience": "http://localhost:5099",
-    "expiryInMinutes": 5
+    "validAudience": "http://localhost:8080",
+    "expiryInMinutes": 1200
   },
   "ApiConfiguration": {
-    "BaseAddress": "http://localhost:5099"
+    "BaseAddress": "http://localhost:8080"
   },
   "EmailConfiguration": {
     "From": "1468441589@qq.com",