UI/UX improvements for project creation inputs: batching, staged files summary, and bounded layout #2263

While working on #2262, I noticed several opportunities to improve the user experience on the project creation page, particularly when staging multiple input files. This is a separate proposal from the bug fix in #2262, as it introduces interaction and layout enhancements (and associated CSS) that may need alignment with existing Bulma patterns and project styling conventions. I have put together an experimental branch/PR so maintainers can see and test the improvements in practice.

Proposed Improvements :

• Unbounded list growth pushes form controls off-screen : adding a large batch of input files (or pasting multiple download URLs) expands the column indefinitely. The user loses sight of the pipeline selection, options, and the 'Create' button, requiring constant scrolling up and down.
• No aggregate summary or batch reset : Users have no immediate visibility into total staged file count or combined size before submitting, and clearing all staged files requires deleting each item individually one by one repeatedly clicking making it quite a bit tiresome on a very long list of files
• Layout shift during item deletion : while continuously deleting files, because of the infinitely expanding page, the layout shifts and might cause unreliable clicks on the delete button + when a file name is too large, the delete button itself goes out of the borders, making it unclickable.

please check PR : #2264 for the improvements in practice.