Multi-bridge Phase 2.5: Per-bridge Live Activities

[tashda]

Why

With N bridges connected, Live Activities must be per-bridge. Today both ConnectionLiveActivityCoordinator and OTAUpdateLiveActivityCoordinator run a single activity each — switching bridges replaces the prior activity.

What

• ConnectionActivityAttributes gains bridgeID: UUID.
• ConnectionLiveActivityCoordinator keeps a [BridgeID: LiveActivityController] map and runs N concurrent activities (one per connected bridge).
• OTAUpdateActivityAttributes gains bridgeID. The static identifier becomes "ota-updates-\(bridgeID)". OTAUpdateLiveActivityCoordinator runs N activities, one per bridge with active OTA.
• Both coordinators stop being singletons in spirit (still global instances, but multi-bridge internally).
• Widget UIs display the bridge name prominently.

Files

• Shellbee/LiveActivities/ConnectionActivityAttributes.swift
• Shellbee/LiveActivities/OTAUpdateActivityAttributes.swift
• Shellbee/LiveActivities/ConnectionLiveActivityCoordinator.swift
• Shellbee/LiveActivities/OTAUpdateLiveActivityCoordinator.swift
• Shellbee/LiveActivities/*Widget.swift

Verification

• Trigger OTA on bridge A and bridge B simultaneously via two test centers; confirm two distinct OTA activities visible on lock screen.
• Disconnect bridge A; confirm only A's connection activity ends, B's stays.

Phase

Phase 2 of multi-bridge support. Depends on #2.1.

[tashda]

Implemented in 73ce0b4 (Per-bridge OTA Live Activity attribution).