2.0: mostrar los dos ultimos pasos del onboarding (aha moment + paywall)

completeOnboarding escribia settings.onboardingCompleted al terminar el paso
de platos. Ese flag es el que ContentView observa para cambiar de OnboardingView
a HomeView, asi que el save destruia el flujo antes de que nextStep() pudiera
pintar el paso 5. WeekReadyStepView (el aha moment de la 1.2.0) y PaywallStepView
no se han visto nunca. GA4 lo confirma: 3 onboarding_completed en 28 dias y cero
eventos con step 5 o 6.

Se separa persistir los datos de marcar el onboarding como terminado:
completeOnboarding(markFinished:) commitea platos y plan sin tocar el flag, y el
nuevo finishOnboarding() lo escribe al salir del paywall. HomeView ya difiere su
prompt premium a la segunda sesion, asi que no hay paywall duplicado.

De paso, los nombres de paso en AnalyticsService estaban desalineados: el indice
5 decia "5_paywall" cuando el paso 5 es WeekReady, y el 6 no tenia nombre.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012Ks8uUcMA9mjypVK7F2Pkt

MealMoodTests/OnboardingViewModelTests.swift

@@ -1,4 +1,5 @@
 import XCTest
+import SwiftData
 @testable import MealMood
 
 @MainActor
@@ -41,4 +42,61 @@ final class OnboardingViewModelTests: XCTestCase {
         XCTAssertEqual(vm.addedDishes.count, 1)
         XCTAssertEqual(vm.addedDishes.first?.tagIds, [fallback.id])
     }
+
+    // MARK: Onboarding completion flag
+
+    /// Returns the container, not just its context: releasing the container
+    /// leaves `mainContext` dangling and SwiftData traps on the next access.
+    private func makeContainer() throws -> ModelContainer {
+        let config = ModelConfiguration(isStoredInMemoryOnly: true)
+        return try ModelContainer(
+            for: AppSettings.self, Tag.self, Dish.self, WeekPlan.self, MealSlot.self,
+            ShoppingItem.self,
+            configurations: config
+        )
+    }
+
+    /// Regression: the flag used to be written at the dishes step, which tore the
+    /// flow down before the Week Ready and paywall steps could render — neither
+    /// was ever seen (confirmed in GA4: no step 5/6 events despite completions).
+    func testCompleteOnboardingKeepsFlowOnScreenWhenNotMarkedFinished() throws {
+        let container = try makeContainer()
+        let context = container.mainContext
+        let vm = OnboardingViewModel()
+        vm.newDishName = "Lentils"
+        vm.addDish(defaultTagId: UUID())
+
+        let saved = vm.completeOnboarding(context: context, markFinished: false)
+
+        XCTAssertTrue(saved)
+        let settings = try context.fetch(FetchDescriptor<AppSettings>()).first
+        XCTAssertNotNil(settings)
+        XCTAssertFalse(settings?.onboardingCompleted ?? true,
+                       "The flag must stay false so the last two steps still render")
+        // The data itself is already committed at this point.
+        XCTAssertEqual(try context.fetch(FetchDescriptor<Dish>()).count, 1)
+        XCTAssertEqual(try context.fetch(FetchDescriptor<WeekPlan>()).count, 1)
+    }
+
+    func testFinishOnboardingSetsTheFlag() throws {
+        let container = try makeContainer()
+        let context = container.mainContext
+        let vm = OnboardingViewModel()
+        vm.completeOnboarding(context: context, markFinished: false)
+
+        vm.finishOnboarding(context: context)
+
+        let stored = try context.fetch(FetchDescriptor<AppSettings>()).first
+        XCTAssertTrue(stored?.onboardingCompleted ?? false)
+    }
+
+    func testCompleteOnboardingStillMarksFinishedByDefault() throws {
+        let container = try makeContainer()
+        let context = container.mainContext
+
+        OnboardingViewModel().completeOnboarding(context: context)
+
+        let stored = try context.fetch(FetchDescriptor<AppSettings>()).first
+        XCTAssertTrue(stored?.onboardingCompleted ?? false)
+    }
 }