fix(backend): 全局参数校验友好化-空参格式错误返回400

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

cfc-backend/src/main/java/com/etotem/cfc/config/GlobalExceptionHandler.java

@@ -4,6 +4,10 @@ import com.etotem.cfc.common.Result;
 import javax.servlet.http.HttpServletRequest;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.springframework.dao.DataIntegrityViolationException;
+import org.springframework.http.converter.HttpMessageNotReadableException;
+import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.MissingServletRequestParameterException;
 import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.RestControllerAdvice;
 import org.springframework.web.multipart.MultipartException;
@@ -18,6 +22,41 @@ public class GlobalExceptionHandler {
         return Result.error(400, e.getMessage());
     }
 
+    /** 业务状态流转异常：以 400 + 业务提示返回，不再裸抛 500 */
+    @ExceptionHandler(IllegalStateException.class)
+    public Result<Void> handleIllegalStateException(IllegalStateException e) {
+        return Result.error(400, e.getMessage());
+    }
+
+    /** 请求体缺失/JSON 语法错误/类型不匹配 */
+    @ExceptionHandler(HttpMessageNotReadableException.class)
+    public Result<Void> handleHttpMessageNotReadable(HttpMessageNotReadableException e) {
+        log.warn("请求体解析失败: {}", e.getMessage());
+        return Result.error(400, "请求参数格式错误，请检查请求体 JSON 或字段类型");
+    }
+
+    /** 缺少必填请求参数（@RequestParam 未传） */
+    @ExceptionHandler(MissingServletRequestParameterException.class)
+    public Result<Void> handleMissingParam(MissingServletRequestParameterException e) {
+        return Result.error(400, "缺少必填参数: " + e.getParameterName());
+    }
+
+    /** @Valid 参数校验失败：返回首个字段错误提示 */
+    @ExceptionHandler(MethodArgumentNotValidException.class)
+    public Result<Void> handleMethodArgumentNotValid(MethodArgumentNotValidException e) {
+        if (e.getBindingResult() != null && e.getBindingResult().getFieldError() != null) {
+            return Result.error(400, e.getBindingResult().getFieldError().getDefaultMessage());
+        }
+        return Result.error(400, "参数校验失败");
+    }
+
+    /** 字段缺失/超长/非空约束等数据完整性问题：改为 400 业务提示 */
+    @ExceptionHandler(DataIntegrityViolationException.class)
+    public Result<Void> handleDataIntegrityViolation(DataIntegrityViolationException e, HttpServletRequest request) {
+        log.warn("数据完整性校验失败: uri={}, error={}", request.getRequestURI(), e.getMessage());
+        return Result.error(400, "数据不完整或格式错误：请检查必填字段与字段长度");
+    }
+
     @ExceptionHandler(MultipartException.class)
     public Result<Void> handleMultipartException(MultipartException e, HttpServletRequest request) {
         log.warn("非multipart请求访问文件接口: uri={}, error={}", request.getRequestURI(), e.getMessage());