Remove empty tasksearch_helper.php and its dead load calls

[NAME-ASHWANIYADAV]

Description

tasksearch_helper.php is a completely empty file - it contains only opening and closing PHP tags (<?php ?>) with no functions, constants, or logic. Despite being empty, it is loaded via $this->load->helper('tasksearch') in two controller constructors, adding unnecessary file I/O on every request.

Changes

• Delete openml_OS/helpers/tasksearch_helper.php (empty file)
• Remove $this->load->helper('tasksearch'); from Frontend.php constructor
• Remove $this->load->helper('tasksearch'); from Backend.php constructor

Verification

• Searched the entire codebase with grep -rn "tasksearch" - no other references exist (no function calls, no imports, no tests)
• The helper defines zero functions, so removing it cannot break any callers
• 3 files changed, 5 deletions, 0 additions