Update: 将子项目从 submodule 转为完整内容

- 移除 GovAI, nomifun-tauri, 算力盒子 的 submodule 引用
- 添加所有子项目的完整源代码
- 保留原始 .git 为 .git.bak 备份

GovAI/server/internal/handler/file.go

@@ -0,0 +1,80 @@
+package handler
+
+import (
+	"fmt"
+	"io"
+	"mime"
+	"mime/multipart"
+	"path/filepath"
+	"strings"
+
+	"github.com/enterprise-ai-platform/server/internal/config"
+)
+
+// ValidateFile checks file size, extension, and MIME type.
+// Returns nil if valid, or an error message if invalid.
+func ValidateFile(header *multipart.FileHeader, allowedExtensions []string, maxSize int64) string {
+	if header.Size > maxSize {
+		return fmt.Sprintf("文件大小超出限制，最大支持 %dMB", maxSize/(1024*1024))
+	}
+
+	ext := strings.ToLower(filepath.Ext(header.Filename))
+	if ext != "" {
+		ext = ext[1:] // strip leading "."
+	}
+
+	extAllowed := false
+	for _, e := range allowedExtensions {
+		if strings.EqualFold(e, ext) {
+			extAllowed = true
+			break
+		}
+	}
+	if !extAllowed {
+		return fmt.Sprintf("不支持的文件类型：.%s，仅支持：%s", ext, strings.Join(allowedExtensions, "、"))
+	}
+
+	// Verify MIME type matches extension
+	mimeType := header.Header.Get("Content-Type")
+	if mimeType != "" {
+		extMime, err := mime.ExtensionsByType(mimeType)
+		if err == nil && len(extMime) > 0 {
+			mimeAllowed := false
+			for _, e := range extMime {
+				if strings.EqualFold(strings.TrimPrefix(e, "."), ext) {
+					mimeAllowed = true
+					break
+				}
+			}
+			if !mimeAllowed && !strings.HasPrefix(mimeType, "text/") && !strings.HasPrefix(mimeType, "application/") {
+				return "文件类型与实际内容不匹配"
+			}
+		}
+	}
+
+	return "" // valid
+}
+
+// AllowedDocumentExtensions returns the list of allowed document file extensions.
+func AllowedDocumentExtensions() []string {
+	return []string{"pdf", "docx", "txt", "md", "csv", "xlsx"}
+}
+
+// AllowedDocumentMaxSize returns the max file size for document uploads.
+func AllowedDocumentMaxSize() int64 {
+	return config.MaxFileSize
+}
+
+// ReadAllWithLimit reads all content from r up to maxSize bytes.
+// Returns error if content exceeds maxSize.
+func ReadAllWithLimit(r io.Reader, maxSize int64) ([]byte, error) {
+	limited := &io.LimitedReader{R: r, N: maxSize + 1}
+	data, err := io.ReadAll(limited)
+	if err != nil {
+		return nil, err
+	}
+	if limited.N == 0 {
+		return nil, fmt.Errorf("文件内容超出 %dMB 限制", maxSize/(1024*1024))
+	}
+	return data, nil
+}