2.0: analytics — log onboarding step as String + step_name for GA4 drop-off

GA4 text custom dimensions do not capture numeric params (step showed as
"(not set)"). Log step as String and add a readable step_name so the
onboarding drop-off is queryable. Registered source/environment/step_name
custom dimensions in the GA4 property to match.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Df9kZEUMXPLn4Kb9Zx1f5o

MealMood/Services/AnalyticsService.swift

@@ -107,8 +107,21 @@ enum AnalyticsService {
         logEvent(AnalyticsEvent.onboardingCompleted, parameters: ["dish_count": dishCount])
     }
 
+    // Human-readable names for each onboarding step, indexed by step number.
+    // Keep in sync with the OnboardingView step order.
+    private static let onboardingStepNames = [
+        "0_welcome", "1_meal_windows", "2_weekends",
+        "3_calendar", "4_first_dishes", "5_paywall"
+    ]
+
     static func logOnboardingStepViewed(step: Int) {
-        logEvent(AnalyticsEvent.onboardingStepViewed, parameters: ["step": step])
+        // GA4 text custom dimensions do not capture numeric params (they show as
+        // "(not set)"). Log the step as a String so the drop-off is queryable.
+        let name = step >= 0 && step < onboardingStepNames.count ? onboardingStepNames[step] : "\(step)"
+        logEvent(AnalyticsEvent.onboardingStepViewed, parameters: [
+            "step": "\(step)",
+            "step_name": name
+        ])
     }
 
     static func logAutoAssignUsed(filledSlots: Int, unfilledSlots: Int) {