feat: add Follow Team Mode (Scenario D) for road trip planning

Adds a new planning mode that lets users follow a team's schedule
(home + away games) and builds multi-city routes accordingly.

Key changes:
- New ScenarioDPlanner with team filtering and route generation
- Team picker UI with sport grouping and search
- Fix TravelEstimator 5-day limit (was 2-day) for cross-country routes
- Fix DateInterval end boundary to include games on last day
- Comprehensive test suite covering edge cases:
  - Multi-city routes with adequate/insufficient time
  - Optimal game selection per city for feasibility
  - 5-day driving segment limits
  - Multiple driver scenarios

Enables trips like Houston → Chicago → Anaheim following the Astros.

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

SportsTime/Features/Trip/ViewModels/TripCreationViewModel.swift

@@ -103,6 +103,10 @@ final class TripCreationViewModel {
     var allowRepeatCities: Bool = true
     var selectedRegions: Set<Region> = [.east, .central, .west]
 
+    // Follow Team Mode
+    var followTeamId: UUID?
+    var useHomeLocation: Bool = true
+
     // MARK: - Dependencies
 
     private let planningEngine = TripPlanningEngine()
@@ -133,6 +137,14 @@ final class TripCreationViewModel {
             return !startLocationText.isEmpty &&
                    !endLocationText.isEmpty &&
                    !selectedSports.isEmpty
+
+        case .followTeam:
+            // Need: team selected + valid date range
+            guard followTeamId != nil else { return false }
+            guard endDate > startDate else { return false }
+            // If using home location, need a valid start location
+            if useHomeLocation && startLocationText.isEmpty { return false }
+            return true
         }
     }
 
@@ -148,6 +160,11 @@ final class TripCreationViewModel {
             if startLocationText.isEmpty { return "Enter a starting location" }
             if endLocationText.isEmpty { return "Enter an ending location" }
             if selectedSports.isEmpty { return "Select at least one sport" }
+
+        case .followTeam:
+            if followTeamId == nil { return "Select a team to follow" }
+            if endDate <= startDate { return "End date must be after start date" }
+            if useHomeLocation && startLocationText.isEmpty { return "Enter your home location" }
         }
         return nil
     }
@@ -174,6 +191,25 @@ final class TripCreationViewModel {
         return (earliest, latest)
     }
 
+    /// Teams grouped by sport for Follow Team picker
+    var teamsBySport: [Sport: [Team]] {
+        var grouped: [Sport: [Team]] = [:]
+        for team in dataProvider.teams {
+            grouped[team.sport, default: []].append(team)
+        }
+        // Sort teams alphabetically within each sport
+        for sport in grouped.keys {
+            grouped[sport]?.sort { $0.name < $1.name }
+        }
+        return grouped
+    }
+
+    /// The currently followed team (for display)
+    var followedTeam: Team? {
+        guard let teamId = followTeamId else { return nil }
+        return dataProvider.teams.first { $0.id == teamId }
+    }
+
     // MARK: - Actions
 
     func loadScheduleData() async {
@@ -279,6 +315,19 @@ final class TripCreationViewModel {
                 viewState = .error("Could not resolve start or end location")
                 return
             }
+
+        case .followTeam:
+            // Use provided date range
+            effectiveStartDate = startDate
+            effectiveEndDate = endDate
+
+            // If using home location, resolve it
+            if useHomeLocation && !startLocationText.isEmpty {
+                await resolveLocations()
+                resolvedStartLocation = startLocation
+                resolvedEndLocation = startLocation  // Round trip - same start/end
+            }
+            // Otherwise, planner will use first/last game locations (fly-in/fly-out)
         }
 
         // Ensure we have games data
@@ -307,7 +356,9 @@ final class TripCreationViewModel {
             numberOfDrivers: numberOfDrivers,
             maxDrivingHoursPerDriver: maxDrivingHoursPerDriver,
             allowRepeatCities: allowRepeatCities,
-            selectedRegions: selectedRegions
+            selectedRegions: selectedRegions,
+            followTeamId: followTeamId,
+            useHomeLocation: useHomeLocation
         )
 
         // Build planning request
@@ -380,6 +431,14 @@ final class TripCreationViewModel {
         case .locations:
             // Keep locations, optionally keep selected games
             break
+
+        case .followTeam:
+            // Clear non-follow-team selections
+            startLocationText = ""
+            endLocationText = ""
+            startLocation = nil
+            endLocation = nil
+            mustSeeGameIds.removeAll()
         }
     }