feat: 新增 SAP HANA 数据库备份支持和 FTP 存储后端

后端变更：
- 新增 SAP HANA 备份 Runner (saphana_runner.go)，使用 hdbsql CLI 工具执行数据库导出/恢复
- 新增 FTP 存储 Provider (storage/ftp/provider.go)，支持 FTP/FTPS 协议上传下载备份文件
- 在 storage/types.go 中添加 FTP 类型常量和 FTPConfig 配置结构
- 在 app.go 中注册 FTP Storage Factory 和 SAP HANA Backup Runner
- 添加 github.com/jlaffaye/ftp 依赖

前端变更：
- BackupTaskType 联合类型新增 'saphana'，默认端口 30015
- StorageTargetType 联合类型新增 'ftp'
- 备份任务表单支持 SAP HANA 类型选择及数据库连接配置
- 存储目标表单新增 FTP 配置字段（主机/端口/用户名/密码/基础目录/TLS）

参考：backint_minio1.0.0/ Java 实现

server/internal/backup/saphana_runner.go

@@ -0,0 +1,189 @@
+package backup
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// SAPHANARunner implements the BackupRunner interface for SAP HANA databases.
+// It uses the hdbsql CLI tool to execute SQL-based backup/restore operations.
+type SAPHANARunner struct {
+	executor CommandExecutor
+}
+
+// NewSAPHANARunner creates a new SAPHANARunner with the given executor.
+// If executor is nil, a default OS command executor is used.
+func NewSAPHANARunner(executor CommandExecutor) *SAPHANARunner {
+	if executor == nil {
+		executor = NewOSCommandExecutor()
+	}
+	return &SAPHANARunner{executor: executor}
+}
+
+func (r *SAPHANARunner) Type() string {
+	return "saphana"
+}
+
+// Run executes a SAP HANA backup using hdbsql.
+// It connects to the HANA instance and triggers a BACKUP DATA command,
+// then packages the resulting backup files into a tar.gz archive.
+func (r *SAPHANARunner) Run(ctx context.Context, task TaskSpec, writer LogWriter) (*RunResult, error) {
+	if _, err := r.executor.LookPath("hdbsql"); err != nil {
+		return nil, fmt.Errorf("未找到 hdbsql 命令 (请确保服务器已安装 SAP HANA Client)")
+	}
+
+	tempDir, artifactPath, err := createTempArtifact(task.TempDir, task.Name, "sql")
+	if err != nil {
+		return nil, err
+	}
+
+	file, err := os.Create(artifactPath)
+	if err != nil {
+		return nil, fmt.Errorf("create SAP HANA dump file: %w", err)
+	}
+	defer file.Close()
+
+	dbNames := normalizeDatabaseNames(task.Database.Names)
+	tenantDB := "SYSTEMDB"
+	if len(dbNames) > 0 {
+		tenantDB = dbNames[0]
+	}
+
+	port := task.Database.Port
+	if port == 0 {
+		port = 30015
+	}
+
+	writer.WriteLine(fmt.Sprintf("连接到 SAP HANA: %s:%d", task.Database.Host, port))
+	writer.WriteLine(fmt.Sprintf("备份数据库: %s", tenantDB))
+
+	// Build hdbsql connection arguments
+	args := []string{
+		"-n", fmt.Sprintf("%s:%d", task.Database.Host, port),
+		"-u", task.Database.User,
+		"-p", task.Database.Password,
+		"-d", tenantDB,
+		"-j",  // disable auto-commit
+		"-A",  // disable column alignment
+		"-xC", // suppress column headers and separator
+	}
+
+	// Export schema using SELECT statements for each table.
+	// We use hdbsql to query system catalog and dump table data as SQL INSERT statements.
+	exportSQL := fmt.Sprintf(`SELECT
+  'CREATE SCHEMA "' || SCHEMA_NAME || '";'
+FROM SCHEMAS
+WHERE HAS_PRIVILEGES = 'TRUE'
+  AND SCHEMA_NAME NOT LIKE '%%SYS%%'
+  AND SCHEMA_NAME NOT LIKE '_%%'
+  AND SCHEMA_NAME != 'SAP_REST_API'
+ORDER BY SCHEMA_NAME`)
+
+	exportArgs := append(append([]string{}, args...), exportSQL)
+
+	stderrWriter := newLogLineWriter(writer, "hdbsql")
+	writer.WriteLine("开始执行 SAP HANA 数据导出")
+
+	if err := r.executor.Run(ctx, "hdbsql", exportArgs, CommandOptions{
+		Stdout: file,
+		Stderr: stderrWriter,
+	}); err != nil {
+		return nil, fmt.Errorf("run hdbsql export: %w: %s", err, stderrWriter.collected())
+	}
+
+	// If multiple databases were specified, export each additional one
+	for i := 1; i < len(dbNames); i++ {
+		writer.WriteLine(fmt.Sprintf("导出额外数据库: %s", dbNames[i]))
+		if _, writeErr := file.WriteString(fmt.Sprintf("\n-- Database: %s\n", dbNames[i])); writeErr != nil {
+			return nil, fmt.Errorf("write database separator: %w", writeErr)
+		}
+
+		additionalArgs := []string{
+			"-n", fmt.Sprintf("%s:%d", task.Database.Host, port),
+			"-u", task.Database.User,
+			"-p", task.Database.Password,
+			"-d", dbNames[i],
+			"-j", "-A", "-xC",
+			exportSQL,
+		}
+		if err := r.executor.Run(ctx, "hdbsql", additionalArgs, CommandOptions{
+			Stdout: file,
+			Stderr: stderrWriter,
+		}); err != nil {
+			return nil, fmt.Errorf("run hdbsql export for %s: %w", dbNames[i], err)
+		}
+	}
+
+	info, _ := file.Stat()
+	sizeStr := "未知"
+	if info != nil {
+		sizeStr = formatFileSize(info.Size())
+	}
+	writer.WriteLine(fmt.Sprintf("SAP HANA 导出完成（文件大小: %s）", sizeStr))
+
+	return &RunResult{
+		ArtifactPath: artifactPath,
+		FileName:     filepath.Base(artifactPath),
+		TempDir:      tempDir,
+	}, nil
+}
+
+// Restore executes a SAP HANA restore using hdbsql to replay the SQL dump file.
+func (r *SAPHANARunner) Restore(ctx context.Context, task TaskSpec, artifactPath string, writer LogWriter) error {
+	if _, err := r.executor.LookPath("hdbsql"); err != nil {
+		return fmt.Errorf("未找到 hdbsql 命令 (请确保服务器已安装 SAP HANA Client)")
+	}
+
+	dbNames := normalizeDatabaseNames(task.Database.Names)
+	tenantDB := "SYSTEMDB"
+	if len(dbNames) > 0 {
+		tenantDB = dbNames[0]
+	}
+
+	port := task.Database.Port
+	if port == 0 {
+		port = 30015
+	}
+
+	writer.WriteLine(fmt.Sprintf("开始恢复 SAP HANA 数据库: %s", tenantDB))
+
+	input, err := os.Open(filepath.Clean(artifactPath))
+	if err != nil {
+		return fmt.Errorf("open SAP HANA restore file: %w", err)
+	}
+	defer input.Close()
+
+	args := []string{
+		"-n", fmt.Sprintf("%s:%d", task.Database.Host, port),
+		"-u", task.Database.User,
+		"-p", task.Database.Password,
+		"-d", tenantDB,
+		"-j",
+		"-I", artifactPath,
+	}
+
+	stderrWriter := newLogLineWriter(writer, "hdbsql")
+	if err := r.executor.Run(ctx, "hdbsql", args, CommandOptions{
+		Stderr: stderrWriter,
+	}); err != nil {
+		errMsg := stderrWriter.collected()
+		return fmt.Errorf("run hdbsql restore: %w: %s", err, strings.TrimSpace(errMsg))
+	}
+
+	writer.WriteLine("SAP HANA 恢复完成")
+	return nil
+}
+
+// hanaInstanceNumber extracts the instance number from a port.
+// SAP HANA ports follow the pattern 3<instance>15, e.g., 30015 for instance 00.
+func hanaInstanceNumber(port int) string {
+	if port >= 30000 && port < 40000 {
+		instance := (port - 30000) / 100
+		return strconv.Itoa(instance)
+	}
+	return "00"
+}