Simplify the file conflict dialog

[jancborchardt]

Same as nextcloud-libraries/nextcloud-upload#2151

Our current file conflict dialog (when you upload the same file again) immediately jumps into a very complex "pick files" view.

Based on a mockup by @kra-mo and some discussions.

The improvements:

• "Existing version" has been moved to the left and "New version" to the right. This is swapped from the previous layout as that was confusing – new things are usually on the right.
• The flow for 1 file was simplified by removing the checkboxes altogether, and just going for buttons "Keep both" and "Replace".
• For multiple files, the newer files are all preselected by default. That way people can click "Continue" directly.
• The wording is simplified
• To more easily compare what’s new or what changed between existing and new, whichever date is newer is bolded, and whichever size is larger is bolded.
• A little arrow inbetween each of the versions pointing right from the existing file to the new file helps with visual clarity.
• The icons of the cancel and skip buttons were removed to reduce visual noise.

We could probably simplify the wording even more for the multiple files case, but this PR is also quite big already. :)

Before	After

Mockup by @kra-mo for reference

🤖 AI (if applicable)

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.16%. Comparing base (2ca2c9c) to head (7b7c979).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2540   +/-   ##
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  Coverage   59.16%   59.16%           
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  Files          15       15           
  Lines         453      453           
  Branches       95       94    -1     
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  Hits          268      268           
  Misses        164      164           
  Partials       21       21           

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[kra-mo]

Nice, but some other things that we might as well change:

• "Incoming" I guess means the same as "new"? Probably good to keep the wording consistent.
• It would be nice to also change the padding for the buttons on the bottom to be consistent on the sides and the bottom.

[susnux]

"Incoming" I guess means the same as "new"? Probably good to keep the wording consistent.

Yes incoming are either

• Files to be uploaded (when used for upload conflicts)
• Files to be copied / moved (when used for that action)

[jancborchardt]

@susnux all resolved. :)

@kra-mo adjusted wording (to "new" as it’s much nicer and less technical) and bottom padding.

All fixed