MemPressure v1.4.1

Fix memory leak from popover view tree

The popover's SwiftUI view tree (PopoverView) was created at app launch and held for the process lifetime, even when hidden. Its 5 @ObservedObject subscriptions stayed active on every 2-second monitor tick, causing ~44 MB residency after the first popover open plus ~1.6 MB/hour drift.

After this fix the view tree is created lazily when the popover opens and released when it closes. 24-hour validation: memory drift dropped from 1.6 MB/h to 0.04 MB/h (40× reduction), with no post-wake spikes across 8 sleep cycles.

This is what was causing macOS to occasionally flag MemPressure as a high-energy app — the leak gradually inflated its rolling Energy Impact score until it crossed Apple's threshold.

No visible behavior changes; the cog animation and all other UI is exactly as before.