Review and Refactor

AccountHealthService (with sharing)
  - getOpenCaseCount, getAverageResolutionDays,
    getTotalWonRevenue, getDaysSinceLastActivity
  - getHealthSummary (combines all four)

AccountHealthSummary (wrapper/DTO, @AuraEnabled fields)

AccountHealthController (with sharing)
  - getAccountHealth (@AuraEnabled, cacheable=true, thin — delegates entirely to the service)

Three classes, each with exactly one job — this is Module 26's Single Responsibility Principle, now spanning the full distance from raw SOQL to the LWC boundary.

• Requirements precisely defined? Yes — each metric stated concretely before coding (Lesson 1).
• Service layer UI-agnostic? Yes — no @AuraEnabled anywhere in AccountHealthService itself.
• Sharing reasoned through deliberately? Yes, with sharing, justified explicitly (Lesson 3).
• Field-level security respected? Yes, via WITH USER_MODE and explicit checks (Lesson 3).
• Thin controller? Yes — AccountHealthController delegates entirely (Lesson 4).
• cacheable=true reasoned through? Yes — a read-only method, explicitly justified (Lesson 4).
• Comprehensive tests, including edge cases? Yes — every metric, the combiner, the controller, and zero-data/null-input scenarios (Lessons 5-6).
• Performance considered, even beyond today\'s scope? Yes — the N+1 risk named explicitly for future extension (Lesson 7).

This is the last "single-feature" project of the course — every subsequent project module builds on genuinely new Apex capabilities (integrations, asynchronous processing) not yet introduced. But the shape of how to build a feature well — design, service layer, security, controller, tests, edge cases, performance, review — is now fully established, and every remaining project in this course reuses it without needing to re-explain it from scratch.