Refactor main to use Cobra command line framework and package restructure

Reorganized the Go package structure, moving the main package to 'cmd'. Upgraded the flag library to Cobra for better management of CLI commands. This included moving the X25519 key generation from a flag to its own standalone Cobra command, which improves user interaction and code modularity. This structural change will benefit future additions and code maintainability.

common/common.go

@@ -1,36 +1,2 @@
 // Package common contains common utilities that are shared among other packages.
 package common
-
-import (
-	"crypto/rand"
-	"encoding/base64"
-	"fmt"
-
-	"golang.org/x/crypto/curve25519"
-)
-
-func X25519() {
-	var publicKey []byte
-	privateKey := make([]byte, curve25519.ScalarSize)
-	if _, err := rand.Read(privateKey); err != nil {
-		fmt.Println(err)
-		return
-	}
-
-	// Modify random bytes using algorithm described at:
-	// https://cr.yp.to/ecdh.html.
-	privateKey[0] &= 248
-	privateKey[31] &= 127
-	privateKey[31] |= 64
-
-	publicKey, err := curve25519.X25519(privateKey, curve25519.Basepoint)
-	if err != nil {
-		fmt.Println(err)
-		return
-	}
-
-	output := fmt.Sprintf("Private key: %v\nPublic key: %v",
-		base64.RawURLEncoding.EncodeToString(privateKey),
-		base64.RawURLEncoding.EncodeToString(publicKey))
-	fmt.Println(output)
-}