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/ScenarioPlanner.swift

@@ -22,6 +22,11 @@ enum ScenarioPlannerFactory {
 
     /// Creates the appropriate planner based on the request inputs
     static func planner(for request: PlanningRequest) -> ScenarioPlanner {
+        // Scenario D: User wants to follow a specific team
+        if request.preferences.followTeamId != nil {
+            return ScenarioDPlanner()
+        }
+
         // Scenario B: User selected specific games
         if !request.selectedGames.isEmpty {
             return ScenarioBPlanner()
@@ -38,6 +43,9 @@ enum ScenarioPlannerFactory {
 
     /// Classifies which scenario applies to this request
     static func classify(_ request: PlanningRequest) -> PlanningScenario {
+        if request.preferences.followTeamId != nil {
+            return .scenarioD
+        }
         if !request.selectedGames.isEmpty {
             return .scenarioB
         }