fix: show sync status overlay for accounts

[Rello]

Motivation

• Improve the user menu for multiple accounts by surfacing per-account sync status so accounts with sync problems are easy to spot.

Description

• Expose per-account sync status on the tray user model by adding syncStatusIcon and syncStatusOk properties on User and new roles SyncStatusIconRole/SyncStatusOkRole in UserModel.
• Compute a per-account sync summary in C++ (determineSyncStatus / syncStatusForAccount) using folder sync results and map those to theme icons (ok, error, warning, pause, sync, offline).
• Wire updates from FolderMan::folderSyncStateChange, FolderMan::folderListChanged and AccountState::isConnectedChanged into a new updateSyncStatus() method and emit model dataChanged when the status changes.
• Overlay a non-OK sync status icon on top of account avatars in the user menu QML (UserLine.qml) placing the overlay in the top-left to avoid hiding the user status indicator.

Testing

• No automated tests were executed for this change.

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Codex Task

[github-actions]

Artifact containing the AppImage: nextcloud-appimage-pr-9397.zip

Digest: sha256:d1924694183e3d04b8bd69e72232b5a2d854c97b411e143c6a3c177c8c0cee6d

To test this change/fix you can download the above artifact file, unzip it, and run it.

Please make sure to quit your existing Nextcloud app and backup your data.

[sonarqubecloud]

Quality Gate failed

Failed conditions
1 Security Hotspot
0.0% Coverage on New Code (required ≥ 80%)
10.4% Duplication on New Code (required ≤ 3%)
33 New Code Smells (required ≤ 0)
B Maintainability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

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[Rello]

[Rello]

Account offline example