feat(ui): add sport backgrounds to share cards, achievement filtering, and wizard validation

- Add ShareCardSportBackground with floating sport icons for share cards
- Share cards now show sport-specific backgrounds (single or multiple sports)
- Achievement collection share respects sport filter selection
- Add ability to share individual achievements from detail sheet
- Trip wizard ReviewStep highlights missing required fields in red
- Add FieldValidation model to TripWizardViewModel

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

SportsTime/Features/Trip/Views/Wizard/Steps/ReviewStep.swift

@@ -19,6 +19,7 @@ struct ReviewStep: View {
     let mustStopLocations: [LocationInput]
     let isPlanning: Bool
     let canPlanTrip: Bool
+    let fieldValidation: FieldValidation
     let onPlan: () -> Void
 
     var body: some View {
@@ -30,11 +31,31 @@ struct ReviewStep: View {
 
             VStack(alignment: .leading, spacing: Theme.Spacing.sm) {
                 ReviewRow(label: "Mode", value: planningMode.displayName)
-                ReviewRow(label: "Sports", value: selectedSports.map(\.rawValue).sorted().joined(separator: ", "))
-                ReviewRow(label: "Dates", value: dateRangeText)
-                ReviewRow(label: "Regions", value: selectedRegions.map(\.shortName).sorted().joined(separator: ", "))
-                ReviewRow(label: "Route", value: routePreference.displayName)
-                ReviewRow(label: "Repeat cities", value: allowRepeatCities ? "Yes" : "No")
+                ReviewRow(
+                    label: "Sports",
+                    value: selectedSports.isEmpty ? "Not selected" : selectedSports.map(\.rawValue).sorted().joined(separator: ", "),
+                    isMissing: fieldValidation.sports == .missing
+                )
+                ReviewRow(
+                    label: "Dates",
+                    value: dateRangeText,
+                    isMissing: fieldValidation.dates == .missing
+                )
+                ReviewRow(
+                    label: "Regions",
+                    value: selectedRegions.isEmpty ? "Not selected" : selectedRegions.map(\.shortName).sorted().joined(separator: ", "),
+                    isMissing: fieldValidation.regions == .missing
+                )
+                ReviewRow(
+                    label: "Route",
+                    value: routePreference.displayName,
+                    isMissing: fieldValidation.routePreference == .missing
+                )
+                ReviewRow(
+                    label: "Repeat cities",
+                    value: allowRepeatCities ? "Yes" : "No",
+                    isMissing: fieldValidation.repeatCities == .missing
+                )
 
                 if !mustStopLocations.isEmpty {
                     ReviewRow(label: "Must-stops", value: mustStopLocations.map(\.name).joined(separator: ", "))
@@ -83,26 +104,33 @@ private struct ReviewRow: View {
     @Environment(\.colorScheme) private var colorScheme
     let label: String
     let value: String
+    var isMissing: Bool = false
 
     var body: some View {
         HStack(alignment: .top) {
             Text(label)
                 .font(.caption)
-                .foregroundStyle(Theme.textMuted(colorScheme))
+                .foregroundStyle(isMissing ? .red : Theme.textMuted(colorScheme))
                 .frame(width: 80, alignment: .leading)
 
             Text(value)
                 .font(.subheadline)
-                .foregroundStyle(Theme.textPrimary(colorScheme))
+                .foregroundStyle(isMissing ? .red : Theme.textPrimary(colorScheme))
 
             Spacer()
+
+            if isMissing {
+                Image(systemName: "exclamationmark.circle.fill")
+                    .font(.caption)
+                    .foregroundStyle(.red)
+            }
         }
     }
 }
 
 // MARK: - Preview
 
-#Preview {
+#Preview("All Valid") {
     ReviewStep(
         planningMode: .dateRange,
         selectedSports: [.mlb, .nba],
@@ -114,6 +142,38 @@ private struct ReviewRow: View {
         mustStopLocations: [],
         isPlanning: false,
         canPlanTrip: true,
+        fieldValidation: FieldValidation(
+            sports: .valid,
+            dates: .valid,
+            regions: .valid,
+            routePreference: .valid,
+            repeatCities: .valid
+        ),
+        onPlan: {}
+    )
+    .padding()
+    .themedBackground()
+}
+
+#Preview("Missing Fields") {
+    ReviewStep(
+        planningMode: .dateRange,
+        selectedSports: [],
+        startDate: Date(),
+        endDate: Date().addingTimeInterval(86400 * 7),
+        selectedRegions: [],
+        routePreference: .balanced,
+        allowRepeatCities: false,
+        mustStopLocations: [],
+        isPlanning: false,
+        canPlanTrip: false,
+        fieldValidation: FieldValidation(
+            sports: .missing,
+            dates: .valid,
+            regions: .missing,
+            routePreference: .valid,
+            repeatCities: .missing
+        ),
         onPlan: {}
     )
     .padding()