test: add StudyHomeViewModel unit tests with DI (IOS-INFO-037)
- Add 6 service protocols (SessionServicing, ReviewServicing,
KBListServicing, QuizListServicing, ActivityHomeServicing,
ContinueLearningServicing)
- ViewModel init supports DI with defaults to .shared
- 16 tests: initial state, loadAll stats, all 5 priority levels
(continueSession→todaysReview→selfTest→startLearning→empty),
banner, weekly stats from summary/streak
- Priority P1 continueSession tested with mock API + temp file
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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