fix(ui): tighten routine preview polish

ui/src/components/EnvVarEditor.tsx

@@ -174,14 +174,13 @@ export function EnvVarEditor({
     // Fill the trailing empty row (or append one) with this secret bound.
     const next = rows.map((row) => ({ ...row }));
     const trailing = next[next.length - 1];
-    const target =
-      trailing && !trailing.key && !trailing.plainValue && !trailing.secretId
-        ? trailing
-        : (() => {
-            const fresh = emptyRow();
-            next.push(fresh);
-            return fresh;
-          })();
+    let target: Row;
+    if (trailing && !trailing.key && !trailing.plainValue && !trailing.secretId) {
+      target = trailing;
+    } else {
+      target = emptyRow();
+      next.push(target);
+    }
     target.source = "secret";
     target.secretId = secret.id;
     target.version = "latest";

ui/src/lib/cron-fires.ts

@@ -198,8 +198,8 @@ export function nextCronFires(
   cursor.setUTCMinutes(cursor.getUTCMinutes() + 1);
 
   const fires: Date[] = [];
-  // Search window: 5 years of minutes is plenty and bounds impossible schedules.
-  const maxIterations = 5 * 366 * 24 * 60;
+  // Preview-only bound: cap sparse or impossible schedules before they can stall the UI.
+  const maxIterations = 2 * 366 * 24 * 60;
   for (let i = 0; i < maxIterations && fires.length < count; i++) {
     let parts: ZonedParts;
     try {