feat(recent-files): allow configuring image grouping

[cristianscheid]

• Resolves: #

Summary

New settings have been added to the Files settings page allowing users to configure image grouping in the Recent Files view.

Behaviour

• Grouping only occurs in the Recent Files view when this option is enabled
• When an image upload is detected, a time window opens from its timestamp with a duration defined in the settings
  • Subsequent images uploaded within that window are collected into the same group
  • If a non-image file is uploaded within the active time window, grouping is suppressed and no group is formed for that batch
  • Once the window closes or is suppressed, the next uploaded image starts a fresh time window
  • This process repeats for the entire list, producing as many groups as the data allows
• Groups can be expanded or collapsed to show/hide individual images
• Selecting a group selects all images within it, with indeterminate state when partially selected

Visuals

demo.webm

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[cristianscheid]

/compile