refactor(service): 统一 VARCHAR 长度为 255，移除 device_id 特殊处理

- DEFAULT_VARCHAR_LENGTH 38 → 255
- 删除 DEVICE_ID_VARCHAR_LENGTH 常量
- 删除 getColumnTypeForDDL 中 device_id 的 VARCHAR(32) 特殊分支
- 删除 formatValue 中 device_id 的 UUID 去连字符逻辑
- 同步更新相关单元测试断言

iot-platform/src/main/java/com/iot/platform/service/TdEngineService.java

     // 默认批量大小
     private static final int DEFAULT_BATCH_SIZE = 50;
 
-    // device_id 字段长度限制
-    private static final int DEVICE_ID_VARCHAR_LENGTH = 32;
-
     // 默认 VARCHAR 字段长度限制
-    private static final int DEFAULT_VARCHAR_LENGTH = 38;
+    private static final int DEFAULT_VARCHAR_LENGTH = 255;
 
     // 东八区时区偏移（避免重复创建）
     private static final ZoneOffset ZONE_OFFSET_8 = ZoneOffset.of("+8");
      * 根据 TdEngine 列类型获取创建列的 SQL 类型
      */
     private String getColumnTypeForDDL(String tdType, String columnName) {
-        // device_id 固定 32，兼容旧表（旧表为 VARCHAR(32)）
-        if ("device_id".equalsIgnoreCase(columnName)) {
-            return "VARCHAR(" + DEVICE_ID_VARCHAR_LENGTH + ")";
-        }
         switch (tdType) {
             case "BOOL":
             case "BIGINT":
         }
 
         // 字符串类型校验长度
-        int maxLen = "device_id".equalsIgnoreCase(columnName) ? DEVICE_ID_VARCHAR_LENGTH : DEFAULT_VARCHAR_LENGTH;
-        if ("device_id".equalsIgnoreCase(columnName)) {
-            // UUID 去掉连字符适配旧表 VARCHAR(32)
-            if (strValue.length() == 36 && strValue.charAt(8) == '-' && strValue.charAt(13) == '-'
-                    && strValue.charAt(18) == '-' && strValue.charAt(23) == '-') {
-                strValue = strValue.replace("-", "");
-                log.debug("device_id UUID 去连字符: {} -> {}", value, strValue);
-            }
-        }
-        if (strValue.length() > maxLen) {
+        if (strValue.length() > DEFAULT_VARCHAR_LENGTH) {
             log.debug("字段值超长，截断存储 | 列: {} | 值长度: {} | 最大: {} | 截断后: {}...",
-                    columnName, strValue.length(), maxLen, strValue.substring(0, maxLen));
-            strValue = strValue.substring(0, maxLen);
+                    columnName, strValue.length(), DEFAULT_VARCHAR_LENGTH, strValue.substring(0, DEFAULT_VARCHAR_LENGTH));
+            strValue = strValue.substring(0, DEFAULT_VARCHAR_LENGTH);
         }
         return "'" + escapeValue(strValue) + "'";
     }

iot-platform/src/test/java/com/iot/platform/service/TDengineServiceTest.java

     }
 
     @Test
-    @DisplayName("getColumnTypeForDDL: VARCHAR 返回 VARCHAR(38)")
+    @DisplayName("getColumnTypeForDDL: VARCHAR 返回 VARCHAR(255)")
     void getColumnTypeForDDL_varchar_returnsWithLength() throws Exception {
         Method method = TdEngineService.class.getDeclaredMethod("getColumnTypeForDDL", String.class, String.class);
         method.setAccessible(true);
 
-        assertThat(method.invoke(tdengineService, "VARCHAR", "col")).isEqualTo("VARCHAR(38)");
-        assertThat(method.invoke(tdengineService, "VARCHAR", "device_id")).isEqualTo("VARCHAR(32)");
+        assertThat(method.invoke(tdengineService, "VARCHAR", "col")).isEqualTo("VARCHAR(255)");
     }
 
     @Test
         Method method = TdEngineService.class.getDeclaredMethod("formatValue", Object.class, String.class, String.class);
         method.setAccessible(true);
 
-        String longStr = "123456789012345678901234567890123456789012345678901234567890123456789"; // 69 chars
+        String longStr = "a".repeat(300);
         assertThat(method.invoke(tdengineService, longStr, "col", "VARCHAR"))
-                .isEqualTo("'12345678901234567890123456789012345678'");
+                .isEqualTo("'" + "a".repeat(255) + "'");
     }
 
     @Test