Replace the browser confirm boxes with undo and in-page dialogs

Three system confirm() dialogs sat in the middle of dealing. The worst was on
Next Hand — the most-pressed button in a session, asking "are you sure?" every
single time, stealing focus and, on a phone, taking over the screen.

Next Hand now just happens, and a toast says where the button landed with an
Undo beside it for the few seconds anyone would notice a misclick. The same
undo covers the pot wizard, which is the more valuable case: paying the wrong
player is a real mistake, and rolling it back restores the hand history entry
and the session standings along with the seats. The snapshot is in-memory only
— an undo is for the mistake you just made, not one from last night.

The two genuinely destructive actions keep a confirmation, but as an in-page
dialog that matches the table instead of the browser's own: Escape or the
backdrop cancels, Enter confirms, and on a phone the buttons go full width with
Cancel nearest the thumb.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_015bnp7xKUPFFSpwkYNFaPgb

JoshHeaps.Net/Pages/Casino/TexasHoldem.cshtml

@@ -210,6 +210,19 @@
     </div>
 </template>
 
+<div id="toastHost" aria-live="polite"></div>
+
+<div id="confirmOverlay" hidden>
+    <div id="confirmModal" role="alertdialog" aria-labelledby="confirmTitle" aria-describedby="confirmMessage" tabindex="-1">
+        <h2 id="confirmTitle"></h2>
+        <p id="confirmMessage"></p>
+        <div class="confirmActions">
+            <button id="confirmCancelBtn" class="holdemBtn holdemBtnGhost" type="button">Cancel</button>
+            <button id="confirmAcceptBtn" class="holdemBtn holdemBtnDanger" type="button">Confirm</button>
+        </div>
+    </div>
+</div>
+
 <div id="potWizardOverlay" hidden>
     <div id="potWizardModal">
         <div class="potWizardHeader">
@@ -226,6 +239,7 @@
 
 @section Scripts {
     <script src="~/js/casino/holdem/money.js?v=@ViewData["cssVersion"]"></script>
+    <script src="~/js/casino/holdem/feedback.js?v=@ViewData["cssVersion"]"></script>
     <script src="~/js/casino/holdem/potCalculator.js?v=@ViewData["cssVersion"]"></script>
     <script src="~/js/casino/holdem/state.js?v=@ViewData["cssVersion"]"></script>
     <script src="~/js/casino/holdem/render.js?v=@ViewData["cssVersion"]"></script>