feat: add ftp root path setting

internal/domain/config.go

@@ -83,6 +83,10 @@ type SSHConfig struct {
 //     reuses the local ssh-agent and ~/.ssh/id_* discovery used by SSH/SCP.
 //   - PathPrefix is relative to the account's login root. The application
 //     rejects absolute paths and traversal segments before uploading.
+//   - RootDirectory is only used to build the path copied to the clipboard.
+//     Keeping it separate from PathPrefix lets the server expose a login root
+//     such as "~/ftp/" while uploads still target a relative directory such
+//     as "snapgo/".
 //   - StrictHostKey and KnownHostsPath apply only to SFTP. Plain FTP has no
 //     host-key mechanism and sends credentials and data without encryption.
 type FTPConfig struct {
@@ -92,6 +96,7 @@ type FTPConfig struct {
 	User               string `json:"user"`
 	AuthMethod         string `json:"authMethod"`
 	Password           string `json:"password"`
+	RootDirectory      string `json:"rootDirectory"`
 	PathPrefix         string `json:"pathPrefix"`
 	StrictHostKey      bool   `json:"strictHostKey"`
 	KnownHostsPath     string `json:"knownHostsPath"`
@@ -260,6 +265,7 @@ func DefaultAppConfig() AppConfig {
 			Protocol:           FTPProtocolFTP,
 			Port:               21,
 			AuthMethod:         SSHAuthPassword,
+			RootDirectory:      "/",
 			PathPrefix:         "snapgo/",
 			ConnectTimeoutSecs: 10,
 			StrictHostKey:      false,
@@ -371,6 +377,13 @@ func (c *AppConfig) Normalize() {
 	if c.FTP.AuthMethod != SSHAuthPassword && c.FTP.AuthMethod != SSHAuthKey {
 		c.FTP.AuthMethod = SSHAuthPassword
 	}
+	if c.FTP.RootDirectory == "" {
+		if c.FTP.Protocol == FTPProtocolSFTP {
+			c.FTP.RootDirectory = "~/"
+		} else {
+			c.FTP.RootDirectory = "/"
+		}
+	}
 	if c.FTP.PathPrefix == "" {
 		c.FTP.PathPrefix = "snapgo/"
 	}