Recently Added survives app restart and is configurable in Settings

[tashda]

Summary

Two issues with the device list's "Recently Added" section that landed together:

1. Section disappeared on every app restart. AppStore persists deviceFirstSeen to UserDefaults precisely so the 30-minute window survives restarts, but AppStore.reset() was clearing both the in-memory map and the UserDefaults entry. ConnectionSessionController.connect() calls reset() on every connection attempt — including the auto-reconnect on app launch — so the persisted state was wiped before any UI saw it.
2. Window length wasn't user-configurable. 30 minutes was hard-coded in AppConfig.UX.recentDeviceWindow. Users with high pairing volumes wanted longer; users who rarely pair wanted shorter.

Fix (commit on dev)

• AppStore.reset() no longer touches deviceFirstSeen or its UserDefaults entry. The 30-minute (or user-chosen) window in DeviceListViewModel already self-prunes the visible list.
• Settings → General → Devices → Recently Added Window picker: 5 min / 15 min / 30 min (default) / 1 hour / 2 hours / 4 hours / 1 day. Stored under DeviceList.recentWindowMinutes. DeviceListViewModel.recentWindow reads the value on each render so changes apply immediately.
• The picker only governs window length. Visibility stays a separate concern handled by the existing "Show Recents" toggle in the device list's Sort menu — single source of truth.

Acceptance criteria

• Pair a device, force-quit and relaunch the app — the device is still in "Recently Added".
• Change the window in Settings → the device list updates without a restart.
• "Show Recents" toggle still hides the section regardless of window length.

[tashda]

Shipped in v1.4.0 (PR #44, tag v1.4.0). Issue was filed retroactively after the fix landed on dev, so the PR body's Closes ref didn't auto-resolve.