Track session standings so the dealer can settle up at the end of the night

The hand log answered "what happened in hand 12"; it couldn't answer "what
does Alice owe". Each resolved pot now records a per-seat ledger (what that
player put in, what they took down) alongside the payouts, and a Session
Standings panel sums it into one row per player — paid in, won, net, sorted
by who's up. The CSV export carries the same table, so one file covers both
the hand-by-hand trail and the cash-out numbers.

Keyed by seat id rather than name, so renaming or reseating a player doesn't
split their totals. Hands recorded before this change have no ledger and are
skipped rather than counted wrong.

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

JoshHeaps.Net/Pages/Casino/TexasHoldem.cshtml

@@ -86,6 +86,22 @@
                 </div>
             </details>
 
+            <details class="sidebarPanel">
+                <summary>Session Standings</summary>
+                <div class="panelBody">
+                    <div id="standingsTable">
+                        <div class="standingsRow standingsHeader">
+                            <span>Player</span>
+                            <span>In</span>
+                            <span>Won</span>
+                            <span>Net</span>
+                        </div>
+                        <div id="standingsList"></div>
+                    </div>
+                    <p id="standingsEmptyHint" class="fieldHint">Once you resolve a pot, everyone's running total for the night shows up here.</p>
+                </div>
+            </details>
+
             <details class="sidebarPanel">
                 <summary>Hand History</summary>
                 <div class="panelBody">
@@ -169,6 +185,15 @@
     </div>
 </template>
 
+<template id="standingsRowTemplate">
+    <div class="standingsRow">
+        <span class="standingsName"></span>
+        <span class="standingsIn"></span>
+        <span class="standingsWon"></span>
+        <span class="standingsNet"></span>
+    </div>
+</template>
+
 <template id="handHistoryRowTemplate">
     <div class="handHistoryRow">
         <div class="handHistoryRowHeader">