fix(badges): print throughput report — descending sort + UTC timezone fix

Buckets now display newest-first. Naive UTC datetime strings from the
backend are normalized with a Z suffix before parsing so times display
in local browser timezone, matching the badge list.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/events/[event_id]/(badges)/badges/reports/reports_badge_print_throughput.svelte

@@ -33,6 +33,14 @@ function fmt_date(ms: number): string {
     return new Date(ms).toLocaleDateString([], { month: 'short', day: 'numeric' });
 }
 
+// Naive UTC strings from the backend have no timezone indicator — append Z so
+// the browser parses them as UTC and converts to local time, matching the badge list display.
+function parse_utc_ms(dt: string | null | undefined): number {
+    if (!dt) return NaN;
+    const normalized = dt.match(/Z$|[+-]\d{2}:?\d{2}$/) ? dt : dt + 'Z';
+    return new Date(normalized).getTime();
+}
+
 let stats: PrintStats = $derived.by(() => {
     const printed = badge_li.filter((b) => (b.print_count ?? 0) >= 1 && b.print_last_datetime);
     if (!printed.length) {
@@ -41,7 +49,7 @@ let stats: PrintStats = $derived.by(() => {
 
     const bucket_ms = bucket_size * 60 * 1000;
     const times = printed
-        .map((b) => new Date(b.print_last_datetime).getTime())
+        .map((b) => parse_utc_ms(b.print_last_datetime))
         .filter((t) => !isNaN(t));
     if (!times.length) {
         return { buckets: [], total_printed: printed.length, max_count: 1, span_label: '' };
@@ -52,29 +60,33 @@ let stats: PrintStats = $derived.by(() => {
     const start = Math.floor(min_raw / bucket_ms) * bucket_ms;
     const end = Math.ceil((max_raw + 1) / bucket_ms) * bucket_ms;
 
-    const buckets: Bucket[] = [];
+    const raw_buckets: Omit<Bucket, 'date_label'>[] = [];
-    let prev_day = '';
 
     for (let t = start; t < end; t += bucket_ms) {
         const in_bucket = printed.filter((b) => {
-            const bt = new Date(b.print_last_datetime).getTime();
+            const bt = parse_utc_ms(b.print_last_datetime);
             return bt >= t && bt < t + bucket_ms;
         });
         if (in_bucket.length === 0) continue;
 
-        const day = fmt_date(t);
+        raw_buckets.push({
-        const date_label = day !== prev_day ? day : null;
-        prev_day = day;
-
-        buckets.push({
             start_ms: t,
             label: fmt_time(t),
-            date_label,
             count: in_bucket.length,
             badges: in_bucket
         });
     }
 
+    // Newest-first display; re-assign date separators after reversing.
+    raw_buckets.reverse();
+    let prev_day = '';
+    const buckets: Bucket[] = raw_buckets.map((b) => {
+        const day = fmt_date(b.start_ms);
+        const date_label = day !== prev_day ? day : null;
+        prev_day = day;
+        return { ...b, date_label };
+    });
+
     const max_count = Math.max(...buckets.map((b) => b.count), 1);
     const span_label =
         buckets.length > 0