Feature Request: Select and Paste Multiple Clipboard Items

### Feature Description

Add the ability to select multiple clipboard items from the clipboard history and paste them all at once. Currently, users can only paste a single clipboard entry at a time. This feature would introduce a multi-select mode in the clipboard manager, allowing users to choose multiple entries and paste them sequentially or combined into the selected window or text field.

### Use Case

Filling out forms or working with repetitive text often requires copying and pasting multiple pieces of information. The ability to select and paste multiple clipboard items in a single operation would save time and reduce manual copy-paste actions. This is especially useful for automation, bulk data entry, or workflows where multiple pieces of text are repeatedly needed.

### Compositor(s)

Niri

### If Other, please specify

_No response_

### Proposed Solution

• Add a multi-select mode to the clipboard manager.
• Allow users to use checkboxes or shift/ctrl selection to select multiple clipboard entries.
• Provide an option (button or shortcut) to paste all selected entries, either concatenating them or pasting sequentially as separate paste actions.
• Optionally, let users choose delimiter (newline, space, etc.) when combining entries.
• This could be inspired by features in advanced clipboard managers on other platforms.

### Alternatives/Existing Solutions

Some clipboard managers on Windows or macOS offer this functionality (e.g., Ditto, CopyQ). Currently, in DankMaterialShell, users must paste items one by one, which is less efficient.