feat: redesign all share cards, remove unused achievement types, fix sport selector

Redesign trip, progress, and achievement share cards with premium
sports-media aesthetic. Remove unused milestone/context achievement card
types (only used in debug exporter). Fix gold text unreadable in light
mode. Fix sport selector to only show stroke on selected sport.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SportsTimeTests/Export/ShareableContentTests.swift

@@ -25,8 +25,6 @@ struct ShareCardTypeTests {
         #expect(allTypes.contains(.tripSummary))
         #expect(allTypes.contains(.achievementSpotlight))
         #expect(allTypes.contains(.achievementCollection))
-        #expect(allTypes.contains(.achievementMilestone))
-        #expect(allTypes.contains(.achievementContext))
         #expect(allTypes.contains(.stadiumProgress))
     }
 
@@ -45,7 +43,7 @@ struct ShareCardTypeTests {
     /// - Invariant: Count matches expected number
     @Test("Invariant: correct count")
     func invariant_correctCount() {
-        #expect(ShareCardType.allCases.count == 6)
+        #expect(ShareCardType.allCases.count == 4)
     }
 }