Fix day count schema: allow 1-7 days instead of hardcoded 3

The [Length(3,3)] attribute on Itinerary.Days forced exactly 3 days
regardless of user selection (1-7). Changed to [Length(1,7)] to match
the UI range. Also relaxed DayPlan.Activities from [Length(3,3)] to
[Length(3,5)] for richer itineraries.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: mattleibow

10.0/AI/LocalChatClientWithAgents/src/Models/Itinerary.cs

@@ -17,8 +17,8 @@ public record Itinerary
 	[Description("An explanation of how the itinerary meets the person's special requests.")]
 	public required string Rationale { get; init; }
 
-	[Description("A list of day-by-day plans.")]
-	[Length(3, 3)]
+	[Description("A list of day-by-day plans matching the requested number of days.")]
+	[Length(1, 7)]
 	public required List<DayPlan> Days { get; init; }
 
 	public static Itinerary GetExampleTripToJapan() =>
@@ -78,7 +78,7 @@ public record DayPlan
 
 	public required string Destination { get; init; }
 
-	[Length(3, 3)]
+	[Length(3, 5)]
 	public required List<Activity> Activities { get; init; }
 }