Media Library: Improved filtering and more reliable collection updates

Search and filtering improvements

The asset list search action has been renamed to “Find in view”, with a conditionally shown input and improved responsiveness on smaller screens. Empty results from search or filters now show clear feedback with a reset option instead of a blank space.

🐛 Notable bugfixes and improvements

Fixed an issue where adding many assets to a collection (for example during bulk uploads) could trigger rate limits, causing some assets not to appear. Assets now load in batches, with placeholders shown in the grid during upload.