fmt: snap |n| < half a cent to exact 0 — kills $-0.00 from float-residue spend

app/main.py

@@ -380,7 +380,7 @@ function flash(msg, ok) {
   setTimeout(() => { f.className = 'flash'; }, 6000);
 }
 
-function fmt(n) { return '$' + (Number(n) || 0).toFixed(2); }
+function fmt(n) { const v = Math.abs(Number(n)) < 0.005 ? 0 : (Number(n) || 0); return '$' + v.toFixed(2); }
 
 async function loadModels() {
   try {