feat: Add "Clone card" feature for Decker task cards

[Copilot]

• Add clone_task() static method to Decker_Tasks class (PHP backend)
• Add REST API endpoint POST /decker/v1/tasks/{id}/clone with capability checks
• Add "Clone" menu item to task card context menu (class-task.php render_task_menu)
• Add JS handler for clone action in footer-scripts.php and task-card.js
• Add localized strings for clone action in class-decker-public.php
• Add Spanish translations in languages/decker-es_ES.po
• Write unit tests for clone functionality (9 test cases)
• After cloning, open the task modal with the cloned task instead of reloading
• Add missing Spanish translation for 'Task not found.' string
• Regenerate MO file

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[erseco]

@copilot after cloning the task open the modal with the cloned task

[Copilot]

@copilot after cloning the task open the modal with the cloned task

Updated in 0a07190. After cloning, the handler now closes any open task modal and opens it with the cloned task using Bootstrap's hidden.bs.modal event for reliable modal transition. If no modal is open (e.g. cloning from board card), it directly opens the modal with the new task.

[erseco]

@copilot add the Spanish unstranslated strings

[Copilot]

@copilot add the Spanish unstranslated strings

Added in 2a4ec6e. The missing Spanish translation for "Task not found." (with period, used in the clone REST endpoint) has been added to the PO file and the MO file has been regenerated. All strings from the clone feature now have Spanish translations.