As an IT Infrastructure Manager, I want a unified view to plan and manage all maintenance windows across all objects — including multi-object and recurring schedules — so that I have organization-wide visibility and can coordinate maintenance without configuring each object individually.

Description:
Following the great design direction of the new GUI (such as centralized Device Template / Auto-Discovery management and Dependency management), Downtimes should also be managed from a unified view.
Dedicated Calendar / Matrix View: A central dashboard listing all upcoming, active, and past scheduled maintenance windows across all objects (Sensors, Devices, Groups, Probes).
Multi-Object Scheduling: Ability to select multiple objects (or apply tag/group filters) and attach them to a single maintenance schedule/job.
Recurring Maintenance: Support for recurring schedules (e.g., Every 2nd Sunday of the month from 02:00 to 04:00 AM).
This would significantly boost efficiency for larger infrastructure monitoring and provide modern, flexible maintenance management.