fix: unify day boundaries on device-local time, JSON import preview parity

- Limits/streaks/greeting now use device-local days (was hardcoded Europe/London),
  matching dashboard metrics; label copy updated
- JSON imports now go through the same preview/duplicate-detection modal as Excel

src/components/views/SettingsView.tsx

@@ -61,7 +61,7 @@ export function SettingsView({
   return (
     <div className="grid gap-4 xl:grid-cols-[1fr_0.8fr]">
       <div className="grid content-start gap-4">
-        <AppCard title="Limits" subtitle="Personal caps for cans, spend, and stop time (BST)">
+        <AppCard title="Limits" subtitle="Personal caps for cans, spend, and stop time (local time)">
           <LimitsSettingsForm
             limits={userLimits}
             check={limitCheck}