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/shortcuts/shortcuts.go

@@ -0,0 +1,42 @@
+package shortcuts
+
+import (
+	"strings"
+
+	"git.zb-server.de/Sebi/ssh-netbox-wrapper/internal/config"
+)
+
+// Normalize strips configured domain suffixes and optionally hyphens from a hostname.
+// The result is lowercased for case-insensitive comparison.
+func Normalize(name string, cfg config.ShortcutsConfig) string {
+	s := strings.ToLower(name)
+	for _, domain := range cfg.Domains {
+		suffix := strings.ToLower(domain)
+		if !strings.HasPrefix(suffix, ".") {
+			suffix = "." + suffix
+		}
+		if strings.HasSuffix(s, suffix) {
+			s = s[:len(s)-len(suffix)]
+			break
+		}
+	}
+	if cfg.StripHyphens {
+		s = strings.ReplaceAll(s, "-", "")
+	}
+	return s
+}
+
+// MakeNormalizer returns a closure bound to cfg, suitable for Cache.GetByShortcut.
+func MakeNormalizer(cfg config.ShortcutsConfig) func(string) string {
+	return func(name string) string {
+		return Normalize(name, cfg)
+	}
+}
+
+// AliasName returns a shell-safe alias name for the given host.
+// It normalizes the name (strips configured domains and optionally hyphens) then
+// replaces any remaining dots with underscores so the result is a valid identifier.
+func AliasName(name string, cfg config.ShortcutsConfig) string {
+	s := Normalize(name, cfg)
+	return strings.ReplaceAll(s, ".", "_")
+}