Add real-time timecard updates on Earthlight project edit screen

[aultra]

Description

Add Supabase real-time subscription for earthlight_timecard_entries to show live updates when employees clock in/out or entries are modified.

Current Behavior

• Timecard entries loaded once when screen/tab initializes
• No automatic refresh when other users modify timecard entries

Implementation

• Add RealtimeChannel subscription for earthlight_timecard_entries
• Filter to current project (project_uuid = project.id)
• Surgical update handlers (INSERT, UPDATE, DELETE)
• Recalculate hoursByLaborType and summaries on each update
• Handle employee cache misses
• Add debouncing to prevent UI thrashing
• Respect _isSavingLocalChanges flag to prevent echo updates
• Test with multiple users editing same project

Benefits

• Managers see live crew activity on projects
• Immediate visibility when employees clock in/out
• Consistent with existing real-time patterns in the app