feat: add planning tips and grouped trip options sorting

- Add PlanningTips data model with 105 tips across 7 categories
- Wire random tips into HomeView (3 tips per session)
- Add TripOptionsGrouper for grouping by city/game count and mileage
- Update TripOptionsView with sectioned display when sorting
- Recommended and Best Efficiency remain flat lists

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

SportsTimeTests/PlanningTipsTests.swift

@@ -0,0 +1,38 @@
+//
+//  PlanningTipsTests.swift
+//  SportsTimeTests
+//
+
+import Testing
+@testable import SportsTime
+
+struct PlanningTipsTests {
+
+    @Test func allTipsHasAtLeast100Tips() {
+        #expect(PlanningTips.all.count >= 100)
+    }
+
+    @Test func randomReturnsRequestedCount() {
+        let tips = PlanningTips.random(3)
+        #expect(tips.count == 3)
+    }
+
+    @Test func randomReturnsUniqueIds() {
+        let tips = PlanningTips.random(5)
+        let uniqueIds = Set(tips.map { $0.id })
+        #expect(uniqueIds.count == 5)
+    }
+
+    @Test func eachTipHasNonEmptyFields() {
+        for tip in PlanningTips.all {
+            #expect(!tip.icon.isEmpty, "Tip should have icon")
+            #expect(!tip.title.isEmpty, "Tip should have title")
+            #expect(!tip.subtitle.isEmpty, "Tip should have subtitle")
+        }
+    }
+
+    @Test func randomWithCountGreaterThanAvailableReturnsAll() {
+        let tips = PlanningTips.random(1000)
+        #expect(tips.count == PlanningTips.all.count)
+    }
+}