添加PyInstaller打包支持和运行时路径修复

- 创建PyInstaller规范文件和打包脚本
- 修复开发/打包环境路径兼容性问题
- 添加PaddleOCR运行时依赖（opencv-contrib-python, pypdfium2, pyclipper）
- 支持打包后的多进程启动
- 修复图标路径和翻译文件路径
- 清理重复的模型和FFmpeg文件
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/tools/common_tools.py

@@ -38,11 +38,15 @@ def is_video_or_image(filename):
     return file_extension in video_extensions or file_extension in image_extensions
 
 def merge_big_file_if_not_exists(dir, file, man_filename = None):
-    if file not in os.listdir(dir):
-        fs = Filesplit()
-        if man_filename is not None:
-            fs.man_filename = man_filename
-        fs.merge(input_dir=dir)
+    try:
+        if file not in os.listdir(dir):
+            fs = Filesplit()
+            if man_filename is not None:
+                fs.man_filename = man_filename
+            fs.merge(input_dir=dir)
+    except Exception as e:
+        print(f"Warning: Could not merge big file {file} in {dir}: {e}")
+        return False
 
 def get_readable_path(path):
     if sys.platform != 'win32':