feat: implement user generation tracking and GitHub star validation for license key generation

- Added UserGeneration model to track user license generation counts and statuses.
- Introduced validateStar utility to check if a user has starred the project on GitHub.
- Updated license key generation endpoint to validate user star status and manage generation limits.
- Refactored server.js to handle new user generation logic and improved error handling.

server/models/UserGeneration.js

@@ -0,0 +1,35 @@
+const mongoose = require('mongoose');
+const { getNowChinaTimeString } = require('../utils/date');
+
+const userGenerationSchema = new mongoose.Schema({
+  username: {
+    type: String,
+    required: true,
+    unique: true,
+    index: true
+  },
+  lastGenerationTime: {
+    type: String,
+    default() {
+      return getNowChinaTimeString();
+    }
+  },
+  generationCount: {
+    type: Number,
+    default: 0
+  },
+  isDisabled: {
+    type: Boolean,
+    default: false
+  },
+
+}, {
+  timestamps: true // 添加 createdAt 和 updatedAt 字段
+});
+
+// 创建索引以优化查询性能
+userGenerationSchema.index({ username: 1 });
+
+const UserGeneration = mongoose.model('UserGeneration', userGenerationSchema);
+
+module.exports = UserGeneration;