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/Planning/Engine/GameDAGRouter.swift

@@ -546,7 +546,15 @@ enum GameDAGRouter {
             ? max(0, availableHours)
             : Double(daysBetween) * constraints.maxDailyDrivingHours
 
-        return drivingHours <= maxDrivingHoursAvailable && drivingHours <= availableHours
+        let feasible = drivingHours <= maxDrivingHoursAvailable && drivingHours <= availableHours
+
+        // Debug output for rejected transitions
+        if !feasible && drivingHours > 10 {
+            print("🔍 DAG canTransition REJECTED: \(fromStadium.city) → \(toStadium.city)")
+            print("🔍   drivingHours=\(String(format: "%.1f", drivingHours)), daysBetween=\(daysBetween), maxAvailable=\(String(format: "%.1f", maxDrivingHoursAvailable)), availableHours=\(String(format: "%.1f", availableHours))")
+        }
+
+        return feasible
     }
 
     // MARK: - Distance Estimation