fix: parse charset as JSON array instead of line-by-line

internal/captcha/handler.go

@@ -1,9 +1,9 @@
 package captcha
 
 import (
-	"bufio"
 	"bytes"
 	"encoding/base64"
+	"encoding/json"
 	"fmt"
 	"image"
 	"math"
@@ -254,26 +254,25 @@ func ctcDecode(output []float32, charset []string) string {
 
 func (h *Handler) loadCharset() ([]string, error) {
 	charsetPath := filepath.Join(h.modelPath, "CharSets.txt")
-	file, err := os.Open(charsetPath)
+
+	// 读取整个文件
+	data, err := os.ReadFile(charsetPath)
 	if err != nil {
 		return nil, err
 	}
-	defer file.Close()
 
-	charset := make([]string, 0, 6000)
-	scanner := bufio.NewScanner(file)
-	for scanner.Scan() {
-		line := strings.TrimSpace(scanner.Text())
-		if line != "" {
-			charset = append(charset, line)
-		}
+	// 解析 JSON 数组格式
+	var charset []string
+	if err := json.Unmarshal(data, &charset); err != nil {
+		return nil, fmt.Errorf("解析字符集失败: %v", err)
 	}
 
-	result := make([]string, len(charset)+1)
-	result[0] = ""
-	copy(result[1:], charset)
+	// 确保第一个元素是空字符串（CTC blank）
+	if len(charset) == 0 || charset[0] != "" {
+		charset = append([]string{""}, charset...)
+	}
 
-	return result, scanner.Err()
+	return charset, nil
 }
 
 // ===================== Math 数学计算 =====================