feat: add Busy user status support with dedicated icon and server capability detection

[Copilot]

This PR implements support for the new "Busy" user status in the Nextcloud Desktop Client, which is available in recent server releases and promoted via the supports_busy capability.

Changes

Backend Implementation

• Added Busy enum value to UserStatus::OnlineStatus after Away (maintaining enum order)
• Added capability detection via userStatusSupportsBusy() method in Capabilities class that checks for supports_busy in server capabilities
• Implemented server communication with bidirectional string mapping: "busy" ↔ UserStatus::OnlineStatus::Busy
• Added capability caching in OcsUserStatusConnector to track busy support per account
• Added dedicated busy icon support with new statusBusyImageSource() method in Theme class

UI Implementation

• Added conditional Busy button in UserStatusSelector.qml that only appears when userStatusSelectorModel.busyStatusSupported is true
• Positioned Busy button after Away as specified in requirements
• Added busyIcon property to UserStatusSelectorModel that returns the dedicated busy icon
• Implemented capability exposure via busyStatusSupported property that reflects server capability

Icon Implementation

• Uses dedicated user-status-busy.svg provided by the design team
• Added statusBusyImageSource() method to Theme class for proper icon handling
• Busy icon features red color with solid circle design, visually distinct from away status
• Integrated with existing theme system following established patterns

Test Coverage

Added comprehensive tests for the busy capability including:

• Capability detection when supports_busy=true
• Capability detection when supports_busy=false
• Capability detection when supports_busy is missing
• Capability detection when user status is disabled

Behavior

On servers with busy support (supports_busy: true):

[Online]     [Away]      
[Busy]       [Do not disturb]       
[Invisible]  

On servers without busy support:

[Online]     [Away]
[Do not disturb]    [Invisible]

The implementation ensures complete backwards compatibility - on older servers or servers without busy support, the UI remains exactly the same with no busy button shown.

Technical Details

The busy status uses its own dedicated visual identity:

• Uses the dedicated busy icon (Theme::statusBusyImageSource()) with red color (#DB0606) and solid circle design
• Positioned after "Away" in the UI layout
• Properly handled in all switch statements and string conversion functions
• Integrated with the existing capability detection framework

This enables users to set their status to "Busy" when supported by their server, providing better granularity in availability communication with a visually distinct icon that clearly differentiates from the away status.

Fixes #8578.

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[Rello]

@copilot a dedicated user-status-busy.svg file is now available for the new status. use this

[Copilot]

@copilot a dedicated user-status-busy.svg file is now available for the new status. use this

Updated to use the dedicated user-status-busy.svg file. Added statusBusyImageSource() method to Theme class and updated the busy icon to use the red circle design instead of the away icon. Changes committed in cf02f91.

[github-actions]

Artifact containing the AppImage: nextcloud-appimage-pr-8579.zip

SHA256 checksum: 1870ba5b97fbe7461b9068cdc36e70ca8d4793ea103f3394443ea69645469924

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
34.8% Coverage on New Code (required ≥ 80%)
B Maintainability Rating on New Code (required ≥ A)
13 New Code Smells (required ≤ 0)

See analysis details on SonarQube Cloud

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[Rello]