Challenge 2: A Module for Room — Solution

@Module
@InstallIn(SingletonComponent::class)
object DatabaseModule {

    @Provides
    @Singleton
    fun provideAppDatabase(@ApplicationContext context: Context): AppDatabase {
        return Room.databaseBuilder(
            context,
            AppDatabase::class.java,
            "app_database"
        ).build()
    }

    @Provides
    @Singleton
    fun provideTaskDao(database: AppDatabase): TaskDao {
        return database.taskDao()
    }
}

Notes:
- @ApplicationContext context: Context is a special Hilt-provided
  qualifier that supplies the app's Application-level Context
  automatically — using the wrong kind of Context (e.g. an Activity
  Context) for building a database that should outlive any single screen
  would be a real bug, so Hilt provides this specifically-scoped one.
- provideTaskDao(database: AppDatabase) takes the AppDatabase as a
  parameter, and Hilt automatically supplies it from
  provideAppDatabase above — the same dependency-chaining behavior shown
  in the chapter's NetworkModule (provideApiService taking a Retrofit
  parameter).
- This replaces the entire manual companion-object singleton pattern
  from Chapter 3 (@Volatile var INSTANCE, synchronized block) — Hilt's
  own @Singleton annotation guarantees only one AppDatabase instance
  exists for the whole app, without writing that thread-safety logic by
  hand.