fix: stray "0" shown for steps with no timer (v0.52.1)

`{step.timerSeconds && (...)}` renders the literal 0 when timerSeconds is
the number 0 rather than null/undefined — only false/null/undefined skip
rendering in JSX, a bare falsy number doesn't. Some steps ended up with
timerSeconds stored as 0 instead of null (e.g. AI generation filling in a
"default" value for an optional field rather than omitting it), which
this guard then rendered as a bare "0" instead of hiding the timer.

Fixed at all 4 render sites (recipe page, cook mode, both print views) by
coercing to a real boolean (`!!step.timerSeconds`) — makes a stored 0
behave identically to null everywhere it's displayed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/app/(app)/recipes/[id]/page.tsx

@@ -427,7 +427,7 @@ export default async function RecipePage({ params }: Params) {
                     </div>
                     <div className="flex-1 space-y-1 pt-1">
                       <p className="leading-relaxed">{step.instruction}</p>
-                      {step.timerSeconds && (
+                      {!!step.timerSeconds && (
                         <p className="text-xs text-muted-foreground flex items-center gap-1">
                           <Clock className="h-3 w-3" />
                           {step.timerSeconds >= 60