feat: introduce shortcuts and shell hook support

- **Shortcuts**: Add hostname normalization with domain stripping and hyphen folding. Include alias generation for cached hosts.
- **Shell Hook**: Automate 24h cache refresh trigger with shell startup hook. Add install/uninstall commands for bash, zsh, and fish.
- **Wizard**: Extend setup wizard to configure shortcuts (domains, hyphen stripping) and default SSH port.
- **Cache**: Add `GetByShortcut` for resolving hosts via normalized shortcuts. Implement `NeedsRefresh` / `SetRefreshed` logic for refresh timestamps.
- **Tests**: Comprehensive unit tests for shortcuts, hook installation, cache refresh, and alias generation.
- **Docs**: Update README with shortcuts, shell hook, and default SSH port configuration.

internal/ssh/args.go

@@ -86,6 +86,19 @@ func ReplaceHost(args []string, destIdx int, newHost string) []string {
 	return result
 }
 
+// HasPortFlag reports whether a port was specified via -p in args.
+func HasPortFlag(args []string) bool {
+	for i, a := range args {
+		if a == "-p" && i+1 < len(args) {
+			return true
+		}
+		if len(a) > 2 && a[0] == '-' && a[1] == 'p' {
+			return true
+		}
+	}
+	return false
+}
+
 // HasUserFlag reports whether a user was specified via -l in args.
 // Used to avoid overriding an explicit -l with the configured default user.
 func HasUserFlag(args []string) bool {