feat: Implement bulk operations for task management

[BenjaminMichaelis]

Bulk operations for cards have felt like a big benefit, allowing me to tag multiple things at once and similar. This allows users to select multiple cards and perform actions such as adding/removing tags, setting due dates, and deleting cards. It also refactors tag and due date manipulation logic into a shared utility module for improved maintainability and consistency.

Bulk operations feature:

• Added bulk selection mode and state management, enabling users to select multiple cards and perform actions on them.
• Implemented action for deleting cards, adding/removing tags, and setting due dates on selected cards, using shared utility functions for content manipulation.
• Added a new BulkOperationsToolbar component, which provides a UI for bulk actions and appears when cards are selected in selection mode.

Codebase refactoring and utility improvements:

• Extracted tag and due date manipulation logic into a new card-content-utils.js module, providing reusable functions such as addTagToContent, removeTagFromContent, setDueDateInContent, and getTagsFromContent. Existing code in App.jsx now uses these shared utilities.

I think these changes significantly improve the user experience for managing multiple cards and while keeping code maintainability by centralizing content manipulation logic.

[BaldissaraMatheus]

Thanks for the submission, this is actually a lot of work!
I included the following changes:

• Bulk operations toolbar is kept open when selection cards mode is on, but the bulk operation buttons are hidden. Included this change to prevent content layout shift when selecting cards;
• Clear selection doesn't stop selection mode anymore. Did this because it was doing the same as the "Exit selection" button so I thought it was pointless to have 2 buttons doing the same thing;
• Some text and style tweaks to be consistent with the rest of the app.

Other than that it's all great, really appreciate all the work!