feat: add multi-row selection to Batch Download

Preflight checklist

• I searched existing issues and this has not been proposed already.
• I checked the README and this is not already supported.

Component

Desktop GUI (Hydra Download Manager)

Problem

In the Batch Download window, files can be sorted by columns such as name, type and size, but selecting a specific group of files is inconvenient.

Currently I have to check files one by one, or use Check All / Uncheck All.

For example, after sorting by Size, I may want to select only a continuous group of files, such as all files below 100 MB. With a large list, manually checking every file is slow.

Proposed solution

Please add standard desktop-style multi-row selection to the Batch Download table.

Suggested behavior:

• Click: select/highlight one row
• Ctrl + Click: add or remove individual rows from the selection
• Shift + Click: select a continuous range
• Shift + Home / Shift + End: extend the selection to the beginning or end
• Selected rows should be visually highlighted
• Add Check Selected and Uncheck Selected actions

Example:

After sorting the list by Size, I could click the first file below 100 MB, then Shift-click the last file below 100 MB, and use Check Selected.

This would allow large batch lists to be handled much faster.

Alternatives considered

The current alternatives are checking files one by one or using Check All / Uncheck All.

These work for small lists, but they are inefficient when only a specific range of files should be selected from a large batch.

Internet Download Manager and standard desktop file/table interfaces support highlighted multi-selection, which makes this type of workflow much easier.

Platforms this should cover

• Linux
• macOS
• Windows
• Android / iOS (via libhydra)

Additional context

This request is for the Batch Download GUI.

The existing column sorting is already useful. Multi-row highlighting and range selection would work especially well with it.

For example:
Sort by Size -> select a range with Shift + Click or Shift + End -> Check Selected.

No screenshot or video is needed to demonstrate the requested behavior.

Compatibility

• This changes existing behavior (flags, defaults, output format, or the C ABI).

Contribution

• I'm willing to open a pull request implementing this.

Start with the Batch Download desktop GUI and trace the existing table sorting, row checking, and Check All/Uncheck All actions. Use the requested click, Ctrl-click, Shift-click, and Shift-Home/End behavior as the interaction checklist, then verify that selected rows are highlighted and Check Selected/Uncheck Selected operate correctly across the listed desktop platforms.