Remove duplicate checklists functionality

Checklists were duplicating subtasks functionality. Removed:
- Migration for task_checklists table
- TaskChecklistModel
- Checklist methods from TaskService
- Checklist routes from Routes.php
- Checklist controller methods
- Checklist UI section from show.twig
- Checklist JavaScript functions

Updated TASKS_MODULE_ROADMAP.md

app/Database/Migrations/2026-02-08-110006_CreateTaskChecklistsTable.php

@@ -1,59 +0,0 @@
-<?php
-
-namespace App\Database\Migrations;
-
-use CodeIgniter\Database\Migration;
-
-class CreateTaskChecklistsTable extends Migration
-{
-    public function up()
-    {
-        $this->forge->addField([
-            'id' => [
-                'type'           => 'INT',
-                'constraint'     => 11,
-                'unsigned'       => true,
-                'auto_increment' => true,
-            ],
-            'task_id' => [
-                'type'       => 'INT',
-                'constraint' => 11,
-                'unsigned'   => true,
-                'null'       => false,
-            ],
-            'title' => [
-                'type'       => 'VARCHAR',
-                'constraint' => 255,
-                'null'       => false,
-            ],
-            'is_completed' => [
-                'type'       => 'BOOLEAN',
-                'default'    => false,
-            ],
-            'order_index' => [
-                'type'       => 'INT',
-                'constraint' => 11,
-                'default'    => 0,
-            ],
-            'created_at' => [
-                'type' => 'DATETIME',
-                'null' => true,
-            ],
-            'updated_at' => [
-                'type' => 'DATETIME',
-                'null' => true,
-            ],
-        ]);
-        
-        $this->forge->addKey('id', true);
-        $this->forge->addKey('task_id');
-        $this->forge->addForeignKey('task_id', 'tasks', 'id', '', 'CASCADE');
-        
-        $this->forge->createTable('task_checklists');
-    }
-
-    public function down()
-    {
-        $this->forge->dropTable('task_checklists');
-    }
-}