Feature/192 copy semester actions

[Rtyujklop]

Summary

Adds an admin interface for duplicating actions from one semester to another.

Changes

• Added DuplicateSemesterPanel component
• Added duplicate semester API endpoint
• Added frontend API constant
• Connected panel to the Action Editor
• Supports copying actions with a configurable day offset
• Reuses existing action creation logic

Closes #192

[andymeneely]

@Rtyujklop Make sure you add notes from today's meeting here.

[Rtyujklop]

Summary

Provide a streamlined way for admins to copy Actions from one semester into another while allowing customization before the copy occurs. Instead of forcing every Action to be duplicated, users should be able to review, edit, and selectively copy only the Actions they need. This provides a reusable starting point for new semesters while reducing manual setup.

Goals

• Replace the current embedded copy interface with a modal.
• Allow users to select both a source semester and a target semester.
• Display all Actions from the selected source semester.
• Allow selective copying using individual checkboxes and a "Select All" option.
• Allow Action dates to be edited inline before copying.
• Apply a client-side date offset that visibly updates dates before submission.
• Warn users about duplicate Action names already existing in the target semester.
• Validate semester selections and edited dates before copying.
• Provide progress feedback while Actions are being copied.
• Reuse the existing Action duplication backend where possible.

To Do

• Create semester copy modal.
• Add source and target semester selection.
• Display Actions with selectable checkboxes.
• Add "Select All" functionality.
• Allow inline editing of Action dates.
• Implement client-side date offset preview.
• Add duplicate Action detection.
• Validate dates and semester selections.
• Add copy progress feedback.
• Test copying across different semesters and Action types.

[andymeneely]

@Rtyujklop After today's meeting, do we think this is ready for review? Or did you want to make more changes?

[Rtyujklop]

@andymeneely I want to make more changes to it before review.