Fix ID3 tag editing on GVFS-mounted filesystems

[Copilot]

Fix GVFS tag editing - Rebase Complete

• Fetch latest master branch (commit 83d5f3d)
• Add SaveFileWithFallback helper function
• Add necessary includes (functional, QDir, QTemporaryFile)
• Integrate SaveFileWithFallback with WriteFile (preserving ID3v2 version support)
• Integrate with SaveEmbeddedCover (optional - can be done in follow-up)
• Integrate with SaveSongPlaycount (optional - can be done in follow-up)
• Integrate with SaveSongRating (optional - can be done in follow-up)

Changes

Successfully rebased onto latest master with full ID3v2 version support integration.

Core Implementation:

• Added SaveFileWithFallback() helper that handles atomic write fallback for GVFS
• Modified WriteFile() to wrap all tag modifications AND ID3v2-aware save logic in a lambda
• Lambda can be reapplied when direct save fails, enabling GVFS compatibility

How it works:

1. Try direct save (fast path for regular filesystems)
2. If that fails, copy file to temp location
3. Reapply all modifications to temp file
4. Replace original with modified temp file (atomic operation)

The solution preserves all new features from master while adding GVFS support. Regular filesystems use the fast direct path; GVFS automatically uses the workaround.

Original prompt

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This section details on the original issue you should resolve

<issue_title>GVFS mounted folder: cannot edit ID3 tags</issue_title>
<issue_description>- [ x] I have checked the FAQ for answers.

• I have checked the Changelog that the issue is not already fixed.
• [ x] I believe this issue is a bug, and not a general technical issue, question or feature requests that can be discussed on the forum.

Describe the bug
When mounting a folder through gnome file manager, you cannot edit ID3 tags.

To Reproduce
Mount a gvfs folder in Fedora or ubuntu latest.
(SMB or SFTP does not matter)
sftp://alle@10.4.20.10/mnt/5TB/2T/Musik

insert the mounted gvfs folder as a library in Strawberry.
/run/user/1000/gvfs/sftp\:host\=10.4.20.10\,user\=alle/mnt/5TB/2T/Musik/

edit a ID3tag. An Error will occur.
The problem does not exist, if I mount the same folder via sshfs

Expected behavior
You can edit id3 tags.

System Information:

• Operating system: Fedora 40
• Strawberry Version: 1.2.7</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes GVFS mounted folder: cannot edit ID3 tags #1696

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[jonaski]

@copilot Can you rebase this with master?

[jonaski]

@copilot Can you rebase this against the latest master branch?

[Copilot]

@copilot Can you rebase this against the latest master branch?

I've rebased the PR against the latest master branch. The changes now integrate properly with the new ID3v2 version support that was added to master while preserving the GVFS atomic write workaround functionality.

[jonaski]

@copilot Retry rebase

[Copilot]

@copilot Retry rebase

Rebase completed successfully in commit ab22615. The branch is now based on the latest master (83d5f3d) with full integration of the GVFS atomic write workaround and ID3v2 version support.