Refine trends and debug harness; clean up warnings

FuelBoard/FavouritesView.swift

@@ -172,11 +172,13 @@ struct FavouritesView: View {
                 )
             }
             .onAppear {
+#if DEBUG
                 // QA hook: launch with `-showTrends` to open the sheet
                 // without a tap (same pattern as -showKeySheet).
                 if ProcessInfo.processInfo.arguments.contains("-showTrends") {
                     showTrends = true
                 }
+#endif
             }
         }
     }