overview: render windows correctly on non-origin monitors

[kanikamaxxing]

Summary

On a multi-monitor setup where any monitor is positioned at a non-zero virtual-desktop offset, opening the overview on that monitor renders every window thumbnail outside its workspace cell — windows render at their global x position scaled down instead of at their monitor-local position.

Root cause is in AxctlService.qml's monitor mapping: it discards mon.metadata.x, mon.metadata.y, and mon.metadata.transform, so monitorData.x is undefined for every monitor. OverviewWindow.qml's let base = windowData.at[0] - monitorData.x falls back to 0, which only works for a monitor at the origin.

Changes

• AxctlService.qml — extract x, y, transform from mon.metadata into the mapped monitor object (3 lines).
• Overview.qml — drop the per-monitor window filter so each overview shows windows from every monitor, look up each window's own monitor for position math, and compute per-window scale as cell_width / window_monitor_width so cross-monitor windows fit their cell properly instead of being sized for the overview's monitor.
• OverviewWindow.qml — after movetoworkspacesilent on drop, also dispatch moveworkspacetomonitor <ws> <drop_monitor> so windows dropped on monitor A's overview actually land on monitor A regardless of which monitor the workspace was previously bound to. Also adds the missing qs.modules.bar.workspaces import so the existing CompositorData.updateWindowList() call on drag finalize stops throwing ReferenceError.

Test plan

• Dual-monitor setup (DP-1 2560×1440 at x=1920, DP-2 1920×1080 at x=0). Overview on DP-1 — windows render inside their cells, matching DP-2's already-correct behaviour.
• Cross-monitor visibility: windows on DP-2 also show in DP-1's overview (and vice versa), each at correct per-monitor scale.
• Drag a window in DP-1's overview, drop onto a workspace cell — window lands on DP-1's monitor.

Happy to iterate if anything here should land differently. Thanks!

— robin