Add a phone-first Quick Split screen for chopping a pot mid-hand

The dealer table is a two-handed, big-screen tool. A dealer standing over a
chopped pot with a phone in one hand and players waiting needs an answer in
seconds, not a table to set up first — so /casino/texasholdem/quicksplit is
the whole job on one screen: type the pot, tap how many ways, tap the
smallest chip in play, read the payout. Nothing to configure, nothing saved.

It splits in whole chips rather than raw arithmetic, because a dealer can't
push half a chip across the felt: everyone gets the same stack and the
remainder is called out as odd chips going one at a time to the first
players left of the button. A pot that doesn't divide into the chosen
denomination says so instead of quietly hiding the difference.

Money formatting moves out of render.js into its own file so this screen can
use it without pulling in the whole seat/chip UI.

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

JoshHeaps.Net/Pages/Casino.cshtml

@@ -19,6 +19,15 @@
             </div>
         </a>
 
+        <a href="/casino/texasholdem/quicksplit" class="game-card">
+            <div class="game-icon">➗</div>
+            <div class="game-title">Quick Split</div>
+            <div class="game-description">
+                Chop a pot in seconds on your phone — no table setup, just the amount,
+                how many players are splitting it, and the smallest chip in play.
+            </div>
+        </a>
+
         <div class="game-card disabled">
             <div class="game-icon">🎲</div>
             <div class="game-title">Craps</div>