feat(auth): support multiple user roles in JWT and services

- Change JWT access token RoleID claim from int to []int to support multiple roles per user
- Update all token generation and refresh logic to handle multiple role IDs as []int
- Refactor services to return and process multiple role IDs from user_roles table
- Fix OAuth state handling explanation and improve code comments
- Clean up related function signatures and usages for consistency

middleware/jwt.go

@@ -186,7 +186,7 @@ func validateSessionFromDB(sessionID string) (*models.JWTSession, error) {
 			WHERE id = ? AND is_revoked = false
 		`, sessionID).Scan(
 			&session.ID,
-			&session.UserID,
+			&session.UsersID,
 			&session.RefreshTokenHash,
 			&session.UserAgent,
 			&session.IPAddress,