Support system-level Do Not Disturb (DND) mode on Linux and Windows

[mremond]

Summary

Request to add support for system-level Do Not Disturb (DND) mode on Linux and Windows. When the operating system's DND mode is enabled, the client could optionally reflect this automatically.

Proposed Behaviour

• Detect when the OS-level DND mode is active (on Linux and Windows).
• Optionally change the user's presence status to DND automatically when the system DND mode is enabled.
• Suppress notification sounds and visual notifications while system DND is active.
• Make this behaviour optional/configurable.

Context

• Monitoring OS-level DND mode is reportedly not available to apps on macOS, so this request targets Linux and Windows.
• No specific handling for OS DND mode currently exists in the client.
• Pointers or implementation references for other OSs would be welcome.

Expected vs. Actual

• Expected: The client can optionally honour the system DND mode by adjusting presence and suppressing notifications/sounds.
• Actual: No OS DND mode integration exists.