refactor(wizard): show all steps at once with validation gating

- Replace progressive reveal with single fade-in of all steps
- Add canPlanTrip validation requiring all fields before planning
- Disable Plan Trip button until all selections are made
- Simplify ViewModel by removing step-by-step visibility logic
- Update tests for new validation-based approach

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

SportsTime/Features/Trip/ViewModels/TripWizardViewModel.swift

@@ -2,7 +2,7 @@
 //  TripWizardViewModel.swift
 //  SportsTime
 //
-//  ViewModel for progressive-reveal trip wizard.
+//  ViewModel for trip wizard.
 //
 
 import Foundation
@@ -16,7 +16,7 @@ final class TripWizardViewModel {
     var planningMode: PlanningMode? = nil {
         didSet {
             if oldValue != nil && oldValue != planningMode {
-                resetDownstreamFromPlanningMode()
+                resetAllSelections()
             }
         }
     }
@@ -58,49 +58,23 @@ final class TripWizardViewModel {
     var sportAvailability: [Sport: Bool] = [:]
     var isLoadingSportAvailability: Bool = false
 
-    // MARK: - Reveal State (computed)
+    // MARK: - Visibility
 
-    var isPlanningModeStepVisible: Bool { true }
-
-    var isDatesStepVisible: Bool {
+    /// All steps visible once planning mode is selected
+    var areStepsVisible: Bool {
         planningMode != nil
     }
 
-    var isSportsStepVisible: Bool {
-        isDatesStepVisible && hasSetDates
-    }
+    // MARK: - Validation
 
-    var isRegionsStepVisible: Bool {
-        isSportsStepVisible && !selectedSports.isEmpty
-    }
-
-    var isRoutePreferenceStepVisible: Bool {
-        isRegionsStepVisible && !selectedRegions.isEmpty
-    }
-
-    var isRepeatCitiesStepVisible: Bool {
-        isRoutePreferenceStepVisible && hasSetRoutePreference
-    }
-
-    var isMustStopsStepVisible: Bool {
-        isRepeatCitiesStepVisible && hasSetRepeatCities
-    }
-
-    var isReviewStepVisible: Bool {
-        isMustStopsStepVisible
-    }
-
-    /// Combined state for animation tracking
-    var revealState: Int {
-        var state = 0
-        if isSportsStepVisible { state += 1 }
-        if isDatesStepVisible { state += 2 }
-        if isRegionsStepVisible { state += 4 }
-        if isRoutePreferenceStepVisible { state += 8 }
-        if isRepeatCitiesStepVisible { state += 16 }
-        if isMustStopsStepVisible { state += 32 }
-        if isReviewStepVisible { state += 64 }
-        return state
+    /// All required fields must be set before planning
+    var canPlanTrip: Bool {
+        planningMode != nil &&
+        hasSetDates &&
+        !selectedSports.isEmpty &&
+        !selectedRegions.isEmpty &&
+        hasSetRoutePreference &&
+        hasSetRepeatCities
     }
 
     // MARK: - Sport Availability
@@ -137,7 +111,7 @@ final class TripWizardViewModel {
 
     // MARK: - Reset Logic
 
-    private func resetDownstreamFromPlanningMode() {
+    private func resetAllSelections() {
         selectedSports = []
         hasSetDates = false
         selectedRegions = []