Add DailyProgressRepository with aggregation methods for efficient data
access layer. Implement cost-overview endpoint that returns profile cost
summary and daily breakdown for a date range.
Repository Features:
- get_by_date: Query progress for profile on specific date with select_related
- get_aggregates_by_profile: Aggregate totals, averages, and counts for date range
- Explicit None handling with ternary operators (no implicit defaults)
Endpoint Features:
- Date range validation with proper YYYY-MM-DD format checking
- Summary statistics: total days, total feet/ice/cost, averages
- Daily breakdown showing only days with actual progress
- Uses repository layer for clean separation of concerns
Tests:
- 7 unit tests for repository methods (filtering, aggregation, edge cases)
- 6 integration tests for cost-overview endpoint (success, validation, errors)
All code passes ruff and mypy with zero violations.
