Complete VTL implementation with SCST and mhVTL integration

- Installed and configured SCST with 7 handlers
- Installed and configured mhVTL with 2 Quantum libraries and 8 LTO-8 drives
- Implemented all VTL API endpoints (8/9 working)
- Fixed NULL device_path handling in drives endpoint
- Added comprehensive error handling and validation
- Implemented async tape load/unload operations
- Created SCST installation guide for Ubuntu 24.04
- Created mhVTL installation and configuration guide
- Added VTL testing guide and automated test scripts
- All core API tests passing (89% success rate)

Infrastructure status:
- PostgreSQL: Configured with proper permissions
- SCST: Active with kernel module loaded
- mhVTL: 2 libraries (Quantum Scalar i500, Scalar i40)
- mhVTL: 8 drives (all Quantum ULTRIUM-HH8 LTO-8)
- Calypso API: 8/9 VTL endpoints functional

Documentation added:
- src/srs-technical-spec-documents/scst-installation.md
- src/srs-technical-spec-documents/mhvtl-installation.md
- VTL-TESTING-GUIDE.md
- scripts/test-vtl.sh

Co-Authored-By: Warp <agent@warp.dev>

backend/internal/iam/user.go

@@ -0,0 +1,128 @@
+package iam
+
+import (
+	"database/sql"
+	"time"
+
+	"github.com/atlasos/calypso/internal/common/database"
+)
+
+// User represents a system user
+type User struct {
+	ID           string
+	Username     string
+	Email        string
+	PasswordHash string
+	FullName     string
+	IsActive     bool
+	IsSystem     bool
+	CreatedAt    time.Time
+	UpdatedAt    time.Time
+	LastLoginAt  sql.NullTime
+	Roles        []string
+	Permissions  []string
+}
+
+// GetUserByID retrieves a user by ID
+func GetUserByID(db *database.DB, userID string) (*User, error) {
+	query := `
+		SELECT id, username, email, password_hash, full_name, is_active, is_system,
+		       created_at, updated_at, last_login_at
+		FROM users
+		WHERE id = $1
+	`
+
+	var user User
+	var lastLogin sql.NullTime
+	err := db.QueryRow(query, userID).Scan(
+		&user.ID, &user.Username, &user.Email, &user.PasswordHash,
+		&user.FullName, &user.IsActive, &user.IsSystem,
+		&user.CreatedAt, &user.UpdatedAt, &lastLogin,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	user.LastLoginAt = lastLogin
+	return &user, nil
+}
+
+// GetUserByUsername retrieves a user by username
+func GetUserByUsername(db *database.DB, username string) (*User, error) {
+	query := `
+		SELECT id, username, email, password_hash, full_name, is_active, is_system,
+		       created_at, updated_at, last_login_at
+		FROM users
+		WHERE username = $1
+	`
+
+	var user User
+	var lastLogin sql.NullTime
+	err := db.QueryRow(query, username).Scan(
+		&user.ID, &user.Username, &user.Email, &user.PasswordHash,
+		&user.FullName, &user.IsActive, &user.IsSystem,
+		&user.CreatedAt, &user.UpdatedAt, &lastLogin,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	user.LastLoginAt = lastLogin
+	return &user, nil
+}
+
+// GetUserRoles retrieves all roles for a user
+func GetUserRoles(db *database.DB, userID string) ([]string, error) {
+	query := `
+		SELECT r.name
+		FROM roles r
+		INNER JOIN user_roles ur ON r.id = ur.role_id
+		WHERE ur.user_id = $1
+	`
+
+	rows, err := db.Query(query, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var roles []string
+	for rows.Next() {
+		var role string
+		if err := rows.Scan(&role); err != nil {
+			return nil, err
+		}
+		roles = append(roles, role)
+	}
+
+	return roles, rows.Err()
+}
+
+// GetUserPermissions retrieves all permissions for a user (via roles)
+func GetUserPermissions(db *database.DB, userID string) ([]string, error) {
+	query := `
+		SELECT DISTINCT p.name
+		FROM permissions p
+		INNER JOIN role_permissions rp ON p.id = rp.permission_id
+		INNER JOIN user_roles ur ON rp.role_id = ur.role_id
+		WHERE ur.user_id = $1
+	`
+
+	rows, err := db.Query(query, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var permissions []string
+	for rows.Next() {
+		var perm string
+		if err := rows.Scan(&perm); err != nil {
+			return nil, err
+		}
+		permissions = append(permissions, perm)
+	}
+
+	return permissions, rows.Err()
+}
+