feat: add a left rail of every service grouped by space

[MazzMat]

Summary

• Adds a fourth layout, "All services on the left": one compact rail with every service grouped by space.
• Spaces and services stay ordered with the existing sort fields; drag reorders within a group or moves a service to another space.
• Settings already lists the new case. Show service names works on this rail too.

Test plan

• Settings → Layout → All services on the left
• Icons grouped under ──── SERVICE ICON ────; empty spaces show Empty
• Drag a service within a group and across groups; drop on an empty space
• After a cross-space move, only the active service stays highlighted
• Cmd+[ / Cmd+] and Cmd+1–9 walk the flattened rail in this layout only