Refactor: Create shared AttachmentService and AttachmentModel

- Created common AttachmentService for all modules (app/Services/)
- Created common AttachmentModel (app/Models/)
- Created common migration (app/Database/Migrations/)
- Updated Tasks module to use shared AttachmentService
- Added Twig functions: format_filesize(), get_file_icon()
- Removed duplicate TaskAttachmentModel and task_attachments migration
- AttachmentService can be used by any module: task, deal, contact, etc.

app/Database/Migrations/2026-02-08-120000_CreateAttachmentsTable.php

@@ -4,7 +4,7 @@ namespace App\Database\Migrations;
 
 use CodeIgniter\Database\Migration;
 
-class CreateTaskAttachmentsTable extends Migration
+class CreateAttachmentsTable extends Migration
 {
     public function up()
     {
@@ -15,10 +15,15 @@ class CreateTaskAttachmentsTable extends Migration
                 'unsigned'       => true,
                 'auto_increment' => true,
             ],
-            'task_id' => [
+            'entity_type' => [
+                'type'       => 'VARCHAR',
+                'constraint' => 50,
+                'null'       => false,
+                'comment'    => 'Тип сущности: task, deal, contact, etc.',
+            ],
+            'entity_id' => [
                 'type'       => 'INT',
                 'constraint' => 11,
-                'unsigned'   => true,
                 'null'       => false,
             ],
             'file_name' => [
@@ -57,14 +62,14 @@ class CreateTaskAttachmentsTable extends Migration
         ]);
         
         $this->forge->addKey('id', true);
-        $this->forge->addKey('task_id');
-        $this->forge->addForeignKey('task_id', 'tasks', 'id', '', 'CASCADE');
+        $this->forge->addKey(['entity_type', 'entity_id']);
+        $this->forge->addKey('uploaded_by');
         
-        $this->forge->createTable('task_attachments');
+        $this->forge->createTable('attachments');
     }
 
     public function down()
     {
-        $this->forge->dropTable('task_attachments');
+        $this->forge->dropTable('attachments');
     }
 }