feat: 实现邀请码验证功能

## 功能概述
   - 用户首次使用需验证邀请码才能发起对话
   - 在输入框聚焦和点击示例时触发验证检查
   - 使用弹窗形式展示邀请码输入界面，包含企业端用户提示和微信二维码

   ## 主要变更

   ### 新增文件
   - `services/invitationService.ts`: 邀请码验证服务，处理验证逻辑和状态管理
   - `views/invitationModal.ts`: 邀请码验证弹窗组件（HTML/CSS/JS）
   - `docs/invitation-code-design.md`: 邀请码功能设计文档

   ### 修改文件
   - `extension.ts`: 添加更换邀请码命令，退出登录时清除验证状态
   - `panels/ICHelperPanel.ts`: 添加邀请码验证状态检查和验证消息处理
   - `services/apiClient.ts`: 添加邀请码验证接口调用
   - `types/api.ts`: 添加邀请码相关类型定义
   - `views/inputArea.ts`: 输入框聚焦时触发邀请码验证检查
   - `views/exampleShowcase.ts`: 点击示例时先检查邀请码验证状态
   - `views/webviewContent.ts`: 集成邀请码弹窗到主界面

   ## 技术实现
   - 验证状态保存在 ExtensionContext.globalState 中
   - 使用后端接口 POST /api/invitation/verify 进行验证
   - 弹窗样式适配 VS Code 主题
   - 支持回车键提交验证

src/services/apiClient.ts

@@ -7,7 +7,7 @@ import * as https from 'https';
 import * as http from 'http';
 import { URL } from 'url';
 import { getApiUrl, getConfig } from '../config/settings';
-import type { ToolCallResult, AnswerRequest, ToolResultResponse, AnswerResponse, ToolConfirmResponse, UserInfoResponse } from '../types/api';
+import type { ToolCallResult, AnswerRequest, ToolResultResponse, AnswerResponse, ToolConfirmResponse, UserInfoResponse, InvitationVerifyRequest, InvitationVerifyResponse, InvitationStatusResponse } from '../types/api';
 
 /**
  * HTTP 请求选项
@@ -260,3 +260,27 @@ export async function getCreditBalance(userId: string): Promise<CreditBalanceRes
     timeout: 5000
   });
 }
+
+/**
+ * 验证邀请码
+ * POST /api/invitation/verify
+ */
+export async function verifyInvitationCode(code: string): Promise<InvitationVerifyResponse> {
+  console.log('[API] 验证邀请码');
+  const body: InvitationVerifyRequest = { code };
+  return request<InvitationVerifyResponse>('/api/invitation/verify', {
+    method: 'POST',
+    body
+  });
+}
+
+/**
+ * 查询邀请码验证状态
+ * GET /api/invitation/status
+ */
+export async function checkInvitationStatus(): Promise<InvitationStatusResponse> {
+  console.log('[API] 查询邀请码验证状态');
+  return request<InvitationStatusResponse>('/api/invitation/status', {
+    method: 'GET'
+  });
+}

src/services/invitationService.ts

@@ -0,0 +1,91 @@
+/**
+ * 邀请码验证服务
+ */
+import * as vscode from 'vscode';
+import { verifyInvitationCode, checkInvitationStatus } from './apiClient';
+
+/**
+ * 邀请码验证服务类
+ */
+export class InvitationService {
+  /**
+   * 检查用户是否已验证邀请码
+   */
+  static async isVerified(context: vscode.ExtensionContext): Promise<boolean> {
+    // 【临时】使用本地验证，不调用后端
+    const localVerified = context.globalState.get<boolean>('invitationCodeVerified');
+    return localVerified || false;
+  }
+
+  /**
+   * 验证邀请码
+   */
+  static async verifyCode(code: string): Promise<{ success: boolean; message: string }> {
+    try {
+      console.log('[InvitationService] 验证邀请码:', code);
+      const response = await verifyInvitationCode(code);
+
+      if (response.code === 200 && response.data?.verified) {
+        return {
+          success: true,
+          message: response.msg || '验证成功'
+        };
+      } else {
+        return {
+          success: false,
+          message: response.msg || '验证失败'
+        };
+      }
+    } catch (error: any) {
+      console.error('[InvitationService] 验证邀请码失败:', error);
+      return {
+        success: false,
+        message: error.message || '网络连接失败，请检查网络后重试'
+      };
+    }
+  }
+
+  /**
+   * 保存验证状态到本地
+   */
+  static async saveVerificationStatus(
+    context: vscode.ExtensionContext,
+    code: string,
+    verifiedTime?: string
+  ): Promise<void> {
+    await context.globalState.update('invitationCodeVerified', true);
+    await context.globalState.update('invitationCode', code);
+    await context.globalState.update('invitationVerifiedTime', verifiedTime || new Date().toISOString());
+  }
+
+  /**
+   * 清除验证状态（用于退出登录或更换邀请码）
+   */
+  static async clearVerificationStatus(context: vscode.ExtensionContext): Promise<void> {
+    await context.globalState.update('invitationCodeVerified', undefined);
+    await context.globalState.update('invitationCode', undefined);
+    await context.globalState.update('invitationVerifiedTime', undefined);
+  }
+
+  /**
+   * 显示邀请码输入弹窗
+   */
+  static async showInputDialog(): Promise<string | undefined> {
+    const code = await vscode.window.showInputBox({
+      prompt: '请输入邀请码以继续使用 IC Coder',
+      placeHolder: '例如：INVITE2024ABC',
+      ignoreFocusOut: true,
+      validateInput: (value) => {
+        if (!value || value.trim().length === 0) {
+          return '邀请码不能为空';
+        }
+        if (value.trim().length < 6) {
+          return '邀请码格式不正确';
+        }
+        return null;
+      }
+    });
+
+    return code?.trim();
+  }
+}