Enhancement: Empty config

When user starts kportal for the first time, and there is no config file,
kportal should create an empty config file with default values and empty
forwarding rules, so that user can easily edit the config file and add their
own rules.

cmd/kportal/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bufio"
 	"context"
 	"flag"
 	"fmt"
@@ -49,6 +50,23 @@ var (
 	appVersion    = "0.1.0" // Set via ldflags during build
 )
 
+// promptCreateConfig asks the user if they want to create a new config file.
+// Returns true if the user answers yes, false otherwise.
+func promptCreateConfig(path string) bool {
+	fmt.Printf("Configuration file not found: %s\n", path)
+	fmt.Print("Would you like to create an empty configuration? [Y/n] ")
+
+	reader := bufio.NewReader(os.Stdin)
+	response, err := reader.ReadString('\n')
+	if err != nil {
+		return false
+	}
+
+	response = strings.TrimSpace(strings.ToLower(response))
+	// Empty response (just Enter) defaults to yes
+	return response == "" || response == "y" || response == "yes"
+}
+
 func main() {
 	flag.Parse()
 
@@ -173,14 +191,38 @@ func main() {
 
 	// Load configuration
 	cfg, err := config.LoadConfig(*configFile)
+	configIsNew := false
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
-		os.Exit(1)
+		if err == config.ErrConfigNotFound {
+			// Config file doesn't exist - offer to create it
+			if !promptCreateConfig(*configFile) {
+				os.Exit(0)
+			}
+			// Create empty config file
+			if err := config.CreateEmptyConfigFile(*configFile); err != nil {
+				fmt.Fprintf(os.Stderr, "Error creating config file: %v\n", err)
+				os.Exit(1)
+			}
+			fmt.Printf("Created %s\n", *configFile)
+			fmt.Println("Use 'n' in the UI to add port forwards, or edit the file manually.")
+			fmt.Println()
+
+			// Load the newly created config
+			cfg, err = config.LoadConfig(*configFile)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
+				os.Exit(1)
+			}
+			configIsNew = true
+		} else {
+			fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
+			os.Exit(1)
+		}
 	}
 
-	// Validate configuration
+	// Validate configuration (allow empty configs for newly created files)
 	validator := config.NewValidator()
-	if errs := validator.ValidateConfig(cfg); len(errs) > 0 {
+	if errs := validator.ValidateConfigWithOptions(cfg, configIsNew || cfg.IsEmpty()); len(errs) > 0 {
 		fmt.Fprint(os.Stderr, config.FormatValidationErrors(errs))
 		os.Exit(1)
 	}