Fix monitoring thresholds, DateTime consistency, and null safety

[markdav-is]

Summary

• Centralized monitoring thresholds: Extracted hardcoded magic numbers (70% survival rate, 30% mortality rate, 2- and 3-month monitoring intervals) into a shared MonitoringThresholds constants class, replacing scattered literals across 4 files
• Fixed DateTime.Now → DateTime.UtcNow: Repository date comparisons used DateTime.Now which produces incorrect results when server timezone differs from data timezone
• Added HttpContext null safety: Prevented potential NullReferenceException in ApplicationService and MonitoringService where HttpContext.User.Identity.Name was accessed without null checks
• Deduplicated intervention logic: Extracted identical intervention-check condition from AddMonitoringSessionAsync and UpdateMonitoringSessionAsync into a shared LogInterventionIfNeeded method
• Removed dead code: Eliminated redundant .ToList() in Garden filter and misleading DateTime.UtcNow default initializer on GardenPhoto.PhotoDate

Files changed

File	Change
Shared/Models/MonitoringThresholds.cs	New — shared constants for monitoring thresholds
Server/Repository/GardenRepository.cs	Use constants + DateTime.UtcNow
Server/Repository/MonitoringRepository.cs	Use constants for mortality threshold
Server/Services/MonitoringService.cs	Null safety + deduplicated intervention check + constants
Server/Services/ApplicationService.cs	Null safety on HttpContext access
Shared/Models/MonitoringModels.cs	Use constants for RequiresIntervention
Shared/Models/GardenModels.cs	Remove DateTime.UtcNow default on PhotoDate
Client/Modules/Garden/Index.razor	Remove redundant .ToList()

Test plan

• Verify garden list loads and "Requires Attention" badges appear for gardens with no monitoring in 2+ months
• Verify garden statistics show "Low survival rate" intervention when average survival < 70%
• Verify monitoring session list flags sessions with mortality > 30%, unhealthy trees, or problems identified
• Verify adding an application as an unauthenticated user does not crash (null safety)
• Verify adding/updating a monitoring session logs intervention warnings when thresholds are exceeded
• Verify garden photo upload still works without a default PhotoDate

https://claude.ai/code/session_0163zLuh4sc1Uf1xWCo91g9y

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[Copilot]

Pull request overview

This PR centralizes monitoring threshold values, improves time-zone correctness by using UTC for date comparisons, and hardens service-layer user identity access to avoid null reference failures.

Changes:

• Introduced MonitoringThresholds constants and replaced scattered magic numbers across server/shared code.
• Switched repository date comparisons from DateTime.Now to DateTime.UtcNow for consistent behavior across time zones.
• Added null-safe HttpContext identity access and deduplicated monitoring intervention logging logic.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
OE.TenTrees/Shared/Models/MonitoringThresholds.cs	Adds shared constants for survival/mortality thresholds and monitoring intervals.
OE.TenTrees/Shared/Models/MonitoringModels.cs	Uses centralized mortality threshold for RequiresIntervention.
OE.TenTrees/Shared/Models/GardenModels.cs	Removes PhotoDate default initializer on GardenPhoto.
OE.TenTrees/Server/Services/MonitoringService.cs	Adds null-safe observer assignment and extracts repeated intervention logging check.
OE.TenTrees/Server/Services/ApplicationService.cs	Adds null-safe applicant/reviewer user ID assignment.
OE.TenTrees/Server/Repository/MonitoringRepository.cs	Uses centralized mortality threshold for RequiresAttention.
OE.TenTrees/Server/Repository/GardenRepository.cs	Uses centralized thresholds and switches monitoring staleness comparisons to UTC.
OE.TenTrees/Client/Modules/Garden/Index.razor	Removes redundant .ToList() during filtering.

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