[stable29] fix(files): ensure valid mtime and fallback to crtime if defined

[backportbot]

Backport of #49225

Warning, This backport's changes differ from the original and might be incomplete ⚠️

Todo

• Review and resolve any conflicts
• Remove all the empty commits

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[skjnldsv]

@solracsf you need to rebase before compiling

[solracsf]

@skjnldsv why /compile rebase doesn't seem to work (at least my attempts always fail...)? 🤔

[skjnldsv]

@skjnldsv why /compile rebase doesn't seem to work (at least my attempts always fail...)? 🤔

depends on the commit history.
If there is one empty commit (like a leftover compile), it might fail to rebase yep

But you can also use GH rebase feature at the bottom (not the merge-update, but the rebase-update)

[skjnldsv]

/compile amend