Complete energy balance calorie target calculations

Complete the energy balance equation implementation for calorie targets across both the wizard flow (EnergyTargetWizard.swift) and the editing flow (EnergyBalanceSettingsSheet.swift). Currently the wizard has ebPreviewMode = true which displays dummy/preview data instead of real user data.

• ●/Users/pxlshpr/Developer/NutriKit/NutriKit/Views/TargetWizard/EnergyTargetWizard.swift - Wizard flow with ebPreviewMode flag at line 86
• ●/Users/pxlshpr/Developer/NutriKit/NutriKit/Refactor Inbox/Views/Maintenance/EnergyBalanceSettingsSheet.swift - Editing flow
• ●/Users/pxlshpr/Developer/NutriKit/NutriKit/Refactor Inbox/Services/MaintenanceCalculator.swift - Core calculation logic
• ●/Users/pxlshpr/Developer/NutriKit/NutriKit/Models/BiometricDay.swift - Data model for daily biometrics

1. Replace Dummy Data with Real Data

• ●Set ebPreviewMode = false in EnergyTargetWizard.swift
• ●Ensure fetchEnergyBalanceData() properly fetches real data from:
  • ●Day model for tracked calories (day.energyInKcal)
  • ●BiometricDay model for weight data
  • ●Apple HealthKit for weight and dietary energy when available
• ●Implement missing HealthKit data fetching in EnergyBalanceSettingsSheet.swift (TODOs at lines 205-208)

2. Verify Calculation Accuracy

The energy balance equation in MaintenanceCalculator.swift:

Maintenance = Average Daily Intake - (Weight Change * 7700 / Days)

Where 7700 kcal ≈ 1 kg of body weight

Ensure both calculation methods work correctly:

• ●calculateEnergyBalance() - uses date range and ModelContext
• ●calculateEnergyBalanceWithBiometricDays() - uses BiometricDay array

3. Handle Edge Cases

Create robust handling for:

• ●Insufficient data: User has only 0-2 days of calorie or weight data
• ●Partial data: User has 50% or fewer days with complete data in the range
• ●No weight change: Start and end weights are identical
• ●Extreme values: Unrealistic calorie intake (< 500 or > 10,000 kcal/day)
• ●Negative maintenance result: Calculation yields negative or extremely low values
• ●Large weight fluctuations: Day-to-day changes > 2kg (likely water weight)
• ●Missing HealthKit permissions: Graceful fallback to manual/app-tracked data
• ●Date range issues: Invalid or reversed date ranges

4. Create Comprehensive Test Suite

Create tests in a new test file EnergyBalanceCalculatorTests.swift covering:

Happy Path Tests:

• ●7-day period with complete calorie and weight data
• ●14-day period with gradual weight loss (maintenance calculation accuracy)
• ●14-day period with gradual weight gain

Edge Case Tests:

• ●Zero days of data - should return nil/error gracefully
• ●Only 1 day of data - should return nil/error
• ●Only 2 days of data - minimum viable calculation
• ●3 days with data in 14-day range (< 50% threshold)
• ●All calories but no weight data
• ●All weight but no calorie data
• ●Mix of data sources (HealthKit + app-tracked + manual)

Boundary Tests:

• ●Extreme calorie values (100 kcal/day, 15,000 kcal/day)
• ●Extreme weight change (5kg loss in 7 days)
• ●Very small weight change (0.1kg over 14 days)
• ●Identical start/end weights
• ●Calculation result below 500 kcal (unrealistic)
• ●Calculation result above 6000 kcal (unrealistic)

Data Source Priority Tests:

• ●Manual overrides HealthKit
• ●App-tracked overrides HealthKit
• ●Excluded days are properly skipped

• ● ebPreviewMode is set to false and real data displays in wizard
• ● Editing flow fetches and displays real data
• ● Calculations match expected results within 1% tolerance
• ● All edge cases display appropriate user-facing messages
• ● Test suite passes with > 90% code coverage on MaintenanceCalculator
• ● No crashes when data is missing or malformed

• ●The BiometricDay model already has isValidForCalculation and isExcludedFromCalculation properties - leverage these
• ●Minimum days required threshold is currently max(3, dayCount / 2) - verify this is appropriate
• ●Consider adding user-facing warnings when data quality is low

Build instruction: Use -destination 'platform=iOS Simulator,name=iPhone 17 Pro' when building this project