perf(backend+frontend): 列表API响应体积优化 3.1MB→145KB (↓95.4%)

- 后端: JPQL构造器投影排除LONGTEXT大字段(uploadedImages/videoReferenceImages)
- 后端: DTO层过滤非分镜图类型的base64内联resultUrl
- 前端: 列表缩略图从video改为img loading=lazy，消除172并发请求
- 前端: download函数增加resultUrl懒加载(详情接口兜底)
- 文档: 新增性能优化报告 docs/performance-optimization-report.md

src/main/java/com/example/demo/config/PayPalConfig.java

@@ -0,0 +1,117 @@
+package com.example.demo.config;
+
+import com.paypal.base.rest.APIContext;
+import com.paypal.base.rest.OAuthTokenCredential;
+import com.paypal.base.rest.PayPalRESTException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * PayPal配置类
+ * 配置PayPal SDK和API上下文
+ */
+@Configuration
+public class PayPalConfig {
+    
+    private static final Logger logger = LoggerFactory.getLogger(PayPalConfig.class);
+    
+    @Value("${paypal.client-id:}")
+    private String clientId;
+    
+    @Value("${paypal.client-secret:}")
+    private String clientSecret;
+    
+    @Value("${paypal.mode:sandbox}")
+    private String mode;
+    
+    @Value("${paypal.success-url:https://vionow.com/api/payment/paypal/success}")
+    private String successUrl;
+    
+    @Value("${paypal.cancel-url:https://vionow.com/api/payment/paypal/cancel}")
+    private String cancelUrl;
+    
+    // CNY到USD的汇率配置，默认7.2（即1美元=7.2人民币）
+    @Value("${paypal.exchange-rate:7.2}")
+    private double exchangeRate;
+    
+    /**
+     * 创建PayPal API上下文
+     * @return API上下文对象
+     */
+    @Bean
+    public APIContext apiContext() {
+        try {
+            // 验证配置
+            if (clientId == null || clientId.isEmpty()) {
+                logger.warn("PayPal Client ID未配置，PayPal功能将不可用");
+                return null;
+            }
+            
+            if (clientSecret == null || clientSecret.isEmpty()) {
+                logger.warn("PayPal Client Secret未配置，PayPal功能将不可用");
+                return null;
+            }
+            
+            logger.info("=== 初始化PayPal配置 ===");
+            logger.info("Client ID: {}...", clientId.substring(0, Math.min(10, clientId.length())));
+            logger.info("Mode: {}", mode);
+            logger.info("Success URL: {}", successUrl);
+            logger.info("Cancel URL: {}", cancelUrl);
+            
+            // 创建PayPal配置
+            Map<String, String> configMap = new HashMap<>();
+            configMap.put("mode", mode);
+            
+            // 创建OAuth凭证
+            OAuthTokenCredential credential = new OAuthTokenCredential(clientId, clientSecret, configMap);
+            
+            // 创建API上下文
+            APIContext context = new APIContext(credential.getAccessToken());
+            context.setConfigurationMap(configMap);
+            
+            logger.info("✅ PayPal配置初始化成功");
+            
+            return context;
+            
+        } catch (PayPalRESTException e) {
+            logger.error("❌ PayPal配置初始化失败", e);
+            logger.error("错误信息: {}", e.getMessage());
+            logger.error("详细错误: {}", e.getDetails());
+            return null;
+        } catch (Exception e) {
+            logger.error("❌ PayPal配置初始化失败", e);
+            return null;
+        }
+    }
+    
+    // Getters
+    public String getClientId() {
+        return clientId;
+    }
+    
+    public String getClientSecret() {
+        return clientSecret;
+    }
+    
+    public String getMode() {
+        return mode;
+    }
+    
+    public String getSuccessUrl() {
+        return successUrl;
+    }
+    
+    public String getCancelUrl() {
+        return cancelUrl;
+    }
+    
+    public double getExchangeRate() {
+        return exchangeRate;
+    }
+}