Added Bulk Actions (Duplicate, Move, Delete) to List View

[cjmalchow]

Hi! I really needed a way to manage multiple items at once, so I built a Bulk Actions bar for the List View.

Resolves #1547

Features included:

• Multi-select checkboxes on the _items_list.html.twig table.
• A hidden action bar that appears when items are selected.
• Duplicate: Clones selected items and appends "(Copy)" to the name, generating a new UUID.
• Move: Fetches a simple list of collections via a new endpoint and moves selected items to the chosen target.
• Delete: Removes selected items.

Note: I am very new to programming! I got this fully functional as a proof-of-concept on my local Docker setup, but I know it might need some polish (like adding CSRF tokens, translations, or moving the JS into a Stimulus controller) to meet your production standards. Let me know what you think!

[cjmalchow]

It's been a month since submitting, and it hasn't been reviewed by Koillections original author yet.