Add random password generation for new users

- Move GenerateRandomPassword to auth package for reuse
- Make password optional in user creation (generates 16-char if empty)
- Return generated password in response for user to copy
- Add Generate/Copy UI with show/hide toggle

backend/internal/auth/jwt.go

@@ -3,8 +3,10 @@
 package auth
 
 import (
-	"errors" // standard errors package
-	"time"   // time handling
+	"crypto/rand" // cryptographically secure random number generator
+	"errors"      // standard errors package
+	"log"         // logging
+	"time"        // time handling
 
 	"github.com/golang-jwt/jwt/v5" // JWT library for token handling
 	"golang.org/x/crypto/bcrypt"   // bcrypt for secure password hashing
@@ -125,3 +127,16 @@ func CheckPassword(password, hash string) bool {
 	err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
 	return err == nil
 }
+
+// GenerateRandomPassword creates a cryptographically secure random password.
+func GenerateRandomPassword(length int) string {
+	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!@#$%^&*"
+	result := make([]byte, length)
+	if _, err := rand.Read(result); err != nil {
+		log.Fatalf("Failed to generate random password: %v", err)
+	}
+	for i := range result {
+		result[i] = charset[int(result[i])%len(charset)]
+	}
+	return string(result)
+}