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/Features/Trip/Views/AddItemSheet.swift

@@ -137,7 +137,7 @@ struct AddItemSheet: View {
             // Search field
             HStack {
                 Image(systemName: "magnifyingglass")
-                    .foregroundStyle(.secondary)
+                    .foregroundStyle(Theme.textMuted(colorScheme))
                     .accessibilityHidden(true)
                 TextField("Search for a place...", text: $searchQuery)
                     .textFieldStyle(.plain)
@@ -155,14 +155,14 @@ struct AddItemSheet: View {
                         selectedPlace = nil
                     } label: {
                         Image(systemName: "xmark.circle.fill")
-                            .foregroundStyle(.secondary)
+                            .foregroundStyle(Theme.textMuted(colorScheme))
                     }
                     .minimumHitTarget()
                     .accessibilityLabel("Clear search")
                 }
             }
             .padding(10)
-            .background(Color(.systemGray6))
+            .background(Theme.cardBackgroundElevated(colorScheme))
             .cornerRadius(10)
 
             // Search results
@@ -181,7 +181,7 @@ struct AddItemSheet: View {
                     }
                 }
                 .frame(maxHeight: 300)
-                .background(Color(.systemBackground))
+                .background(Theme.cardBackground(colorScheme))
                 .cornerRadius(10)
             } else if !searchQuery.isEmpty && !isSearching {
                 Text("No results found")