feat(api): add server IP display for exchange whitelist configuration (#520)

Added functionality to display server public IP address for users to configure exchange API whitelists, specifically for Binance integration.

Backend changes (api/server.go):
- Add GET /api/server-ip endpoint requiring authentication
- Implement getPublicIPFromAPI() with fallback to multiple IP services
- Implement getPublicIPFromInterface() for local network interface detection
- Add isPrivateIP() helper to filter private IP addresses
- Import net package for IP address handling

Frontend changes (web/):
- Add getServerIP() API method in api.ts
- Display server IP in ExchangeConfigModal for Binance
- Add IP copy-to-clipboard functionality
- Load and display server IP when Binance exchange is selected
- Add i18n translations (en/zh) for whitelist IP messages:
  - whitelistIP, whitelistIPDesc, serverIPAddresses
  - copyIP, ipCopied, loadingServerIP

User benefits:
- Simplifies Binance API whitelist configuration
- Shows exact server IP to add to exchange whitelist
- One-click IP copy for convenience

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: tinkle-community <tinklefund@gmail.com>

web/src/lib/api.ts

@@ -327,4 +327,16 @@ export const api = {
     })
     if (!res.ok) throw new Error('保存用户信号源配置失败')
   },
-}
+
+  // 获取服务器IP（需要认证，用于白名单配置）
+  async getServerIP(): Promise<{
+    public_ip: string;
+    message: string;
+  }> {
+    const res = await fetch(`${API_BASE}/server-ip`, {
+      headers: getAuthHeaders(),
+    });
+    if (!res.ok) throw new Error('获取服务器IP失败');
+    return res.json();
+  },
+};