refactor: migrate deprecated .withOpacity() to .withValues(alpha:)

`Color.withOpacity` is deprecated in the pinned Flutter SDK. `withValues`
stores alpha as a double instead of quantising it to 8 bits; `toARGB32()`
rounds to the same byte for every alpha, so nothing renders differently.

83 call sites in 52 files. Reproducible from the preceding commit: substitute
`.withOpacity(X)` -> `.withValues(alpha: X)` and run `dart format`, which
rewraps the 12 sites (10 files) where the longer name no longer fits the line.

Author: sneurlax

lib/notifications/notification_card_layout.dart

@@ -85,7 +85,9 @@ class NotificationCardLayout extends StatelessWidget {
         ),
         if (read)
           Positioned.fill(
-            child: RoundedContainer(color: colors.background.withOpacity(0.5)),
+            child: RoundedContainer(
+              color: colors.background.withValues(alpha: 0.5),
+            ),
           ),
       ],
     );

lib/pages/buy_view/buy_form.dart

@@ -840,7 +840,7 @@ class _BuyFormState extends ConsumerState<BuyForm> {
                       ? Theme.of(context)
                             .extension<StackColors>()!
                             .currencyListItemBG
-                            .withOpacity(_hovering1 ? 0.3 : 0)
+                            .withValues(alpha: _hovering1 ? 0.3 : 0)
                       : Theme.of(
                           context,
                         ).extension<StackColors>()!.textFieldDefaultBG,
@@ -906,7 +906,7 @@ class _BuyFormState extends ConsumerState<BuyForm> {
                       ? Theme.of(context)
                             .extension<StackColors>()!
                             .currencyListItemBG
-                            .withOpacity(_hovering2 ? 0.3 : 0)
+                            .withValues(alpha: _hovering2 ? 0.3 : 0)
                       : Theme.of(
                           context,
                         ).extension<StackColors>()!.textFieldDefaultBG,

lib/pages/buy_view/buy_view.dart

@@ -73,7 +73,7 @@ class _BuyViewState extends ConsumerState<BuyView> {
             Container(
               color: Theme.of(
                 context,
-              ).extension<StackColors>()!.overlay.withOpacity(0.7),
+              ).extension<StackColors>()!.overlay.withValues(alpha: 0.7),
               height: MediaQuery.of(context).size.height,
               width: MediaQuery.of(context).size.width,
               child: const StackDialog(

lib/pages/exchange_view/exchange_coin_selection/exchange_currency_selection_view.dart

@@ -78,7 +78,7 @@ class _ExchangeCurrencySelectionViewState
           child: Container(
             color: Theme.of(
               context,
-            ).extension<StackColors>()!.overlay.withOpacity(0.6),
+            ).extension<StackColors>()!.overlay.withValues(alpha: 0.6),
             child: const CustomLoadingOverlay(
               message: "Loading currencies",
               eventBus: null,

lib/pages/exchange_view/exchange_form.dart

@@ -117,7 +117,7 @@ class _ExchangeFormState extends ConsumerState<ExchangeForm> {
           child: Container(
             color: Theme.of(
               context,
-            ).extension<StackColors>()!.overlay.withOpacity(0.6),
+            ).extension<StackColors>()!.overlay.withValues(alpha: 0.6),
             child: const CustomLoadingOverlay(
               message: "Updating exchange rate",
               eventBus: null,

lib/pages/exchange_view/exchange_loading_overlay.dart

@@ -79,7 +79,7 @@ class _ExchangeLoadingOverlayViewState
           Container(
             color: Theme.of(
               context,
-            ).extension<StackColors>()!.overlay.withOpacity(0.7),
+            ).extension<StackColors>()!.overlay.withValues(alpha: 0.7),
             child: const CustomLoadingOverlay(
               message: "Loading Exchange data",
               eventBus: null,
@@ -92,7 +92,7 @@ class _ExchangeLoadingOverlayViewState
           Container(
             color: Theme.of(
               context,
-            ).extension<StackColors>()!.overlay.withOpacity(0.7),
+            ).extension<StackColors>()!.overlay.withValues(alpha: 0.7),
             child: Column(
               mainAxisAlignment: MainAxisAlignment.end,
               children: [

lib/pages/exchange_view/exchange_step_views/step_3_view.dart

@@ -228,7 +228,7 @@ class _Step3ViewState extends ConsumerState<Step3View> {
                                               color: Theme.of(context)
                                                   .extension<StackColors>()!
                                                   .overlay
-                                                  .withOpacity(0.6),
+                                                  .withValues(alpha: 0.6),
                                               child: const CustomLoadingOverlay(
                                                 message: "Creating a trade",
                                                 eventBus: null,

lib/pages/exchange_view/exchange_view.dart

@@ -96,7 +96,7 @@ class _ExchangeViewState extends ConsumerState<ExchangeView> {
             Material(
               color: Theme.of(
                 context,
-              ).extension<StackColors>()!.overlay.withOpacity(0.6),
+              ).extension<StackColors>()!.overlay.withValues(alpha: 0.6),
               child: const CustomLoadingOverlay(
                 message: "Updating exchange data",
                 subMessage: "This could take a few minutes",

lib/pages/exchange_view/send_from_view.dart

@@ -566,7 +566,7 @@ class _SendFromCardState extends ConsumerState<SendFromCard> {
             children: [
               Container(
                 decoration: BoxDecoration(
-                  color: ref.watch(pCoinColor(coin)).withOpacity(0.5),
+                  color: ref.watch(pCoinColor(coin)).withValues(alpha: 0.5),
                   borderRadius: BorderRadius.circular(
                     Constants.size.circularBorderRadius,
                   ),

lib/pages/exchange_view/wallet_initiated_exchange_view.dart

@@ -113,7 +113,7 @@ class _WalletInitiatedExchangeViewState
             Material(
               color: Theme.of(
                 context,
-              ).extension<StackColors>()!.overlay.withOpacity(0.6),
+              ).extension<StackColors>()!.overlay.withValues(alpha: 0.6),
               child: const CustomLoadingOverlay(
                 message: "Updating exchange data",
                 subMessage: "This could take a few minutes",