feat: enforce custom Theme colors app-wide, add debug sample trips and poll

Replace all system colors (.secondary, Color(.secondarySystemBackground),
etc.) with Theme.textPrimary/textSecondary/textMuted/cardBackground/
surfaceGlow across 13 views. Remove PostHog debug logging. Add debug
settings for sample trips and hardcoded group poll preview.

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

SportsTime/Core/Analytics/AnalyticsManager.swift

@@ -79,7 +79,6 @@ final class AnalyticsManager {
         }
 
         #if DEBUG
-        config.debug = true
         config.flushAt = 1
         #endif