feat: 添加头像下方修改按钮和头像上传功能

- mine.vue: 头像下方添加灰色修改按钮
- api.js: 添加getBaseUrl方法
- UserController.java: 添加uploadAvatar接口
- WebConfig.java: 配置静态文件服务
- 支持修改用户名和上传头像

src/main/java/xuan/config/WebConfig.java

@@ -0,0 +1,15 @@
+package xuan.config;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+@Configuration
+public class WebConfig implements WebMvcConfigurer {
+    
+    @Override
+    public void addResourceHandlers(ResourceHandlerRegistry registry) {
+        registry.addResourceHandler("/uploads/**")
+                .addResourceLocations("file:uploads/");
+    }
+}