feat: add TLS certificate management functionality

- Implemented TLS certificate model and service for managing certificates.
- Added API endpoints for creating, importing, listing, and deleting TLS certificates.
- Enhanced proxy route configuration to support HTTPS with certificate selection.
- Updated frontend to include TLS certificate management UI with manual and file import options.
- Added validation for HTTPS routes to ensure certificates are selected.
- Implemented tests for TLS certificate creation and proxy route validation.

atsf_server/service/tls_certificate_helpers.go

@@ -0,0 +1,34 @@
+package service
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"io"
+	"mime/multipart"
+)
+
+func parseLeafCertificate(certPEM string) (*x509.Certificate, error) {
+	certPEMBlock, _ := pem.Decode([]byte(certPEM))
+	if certPEMBlock == nil {
+		return nil, errors.New("证书 PEM 内容不合法")
+	}
+	leaf, err := x509.ParseCertificate(certPEMBlock.Bytes)
+	if err != nil {
+		return nil, err
+	}
+	return leaf, nil
+}
+
+func readMultipartFile(fileHeader *multipart.FileHeader) (string, error) {
+	file, err := fileHeader.Open()
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+	data, err := io.ReadAll(file)
+	if err != nil {
+		return "", err
+	}
+	return string(data), nil
+}